The memory error is due to lack of DOS conventional memory (the 640kb region.) You need to change your C:\CONFIG.SYS file to free up some conventional memory. Usually, all you need to do is having the line that begins with "DOS=" look like this:

DOS=HIGH,UMB,AUTO

If a line that begins with "DOS=" is not there, add it directly under the line that ends with "EMM386.EXE".

Reboot.

As for the "illegal instruction" error, this can occur if your CPU is way too fast for the game or application you're running. The Pentium 4 might be the cause of this. I'm not sure if there's a good way to slow down this CPU. Other people here might post some ideas.

Edit:
You said your config.sys was empty? That should never happen. You can use this as your C:\CONFIG.SYS:

1device=c:\windows\himem.sys /testmem:off
2device=c:\windows\emm386.exe
3dos=high,umb,auto
4files=60

You can post the contents of your autoexec.bat here so we can tell you how to modify it to free up more conventional memory (needed for DOS games.)

realnc wrote:

You said your config.sys was empty? That should never happen.

I think it was empty, I'll have to check again. I just installed Win98 on this drive, so nothing's really changed other than the drivers I installed. I think Autoexec.bat just had one line, which I removed.

realnc wrote:

As for the "illegal instruction" error, this can occur if your CPU is way too fast for the game or application you're running. The Pentium 4 might be the cause of this. I'm not sure if there's a good way to slow down this CPU. Other people here might post some ideas.

This happens just in Windows itself, when I'm not running any programs or games. What you're saying kind of makes sense, but I've been using Windows 98 on this system for at least a couple years now, and I never encountered this exact problem until just recently. There are ways that I could slow down the CPU - there's a DOS program called Throttle that I've used before with this CPU that seems to work well. I could also underclock it in the BIOS, I think.

The P4 being too fast by itself doesn't really explain this, since, like I said, it wasn't doing this before. But do you think it could be a combination of the P4's speed and the card I added (Matrox m3D) and/or its drivers? Maybe the drivers are doing something in the background even when the card isn't being used, and the CPU being too fast causes it to fail.

I'll try some of the things you suggested tomorrow.

By the way, I listed it in my other thread, but here are the specs of my system:

Pentium 4 "Northwood" 2.53GHz
ASUS P4S533
512MB DDR
Voodoo 3 3000
Matrox m3D
Sound Blaster Live!
250GB HDD
Pioneer slot-loading DVD drive
Sony floppy drive
Windows 98 SE

You could try running the system with less ram and see if that fixes any issues. Win98 doesn't need large amounts of ram and it generally doesn't boot at all above 512Mb, so if you could try putting just 256Mb ram in the system and see if that fixes any of the issues.

Baoran wrote:

You could try running the system with less ram and see if that fixes any issues. Win98 doesn't need large amounts of ram and it generally doesn't boot at all above 512Mb, so if you could try putting just 256Mb ram in the system and see if that fixes any of the issues.

I might try that. I have another memory module, but I don't know if it works or what size it is. I think it might be 256MB, but I'm not sure (it doesn't say on the stick itself). Still, it might be worth a try.

I tried slowing down the CPU, and I tried editing Config.sys: neither of those things fixed the "illegal operation" error. I haven't tried running the Windows installer again, but I'm no longer concerned about that; I mainly just want to solve the "illegal operation" error. I haven't tried different memory yet, but I'm kinda doubtful that's the issue. Any other ideas?

GordonFreeman wrote:

I tried slowing down the CPU, and I tried editing Config.sys: neither of those things fixed the "illegal operation" error. I haven't tried running the Windows installer again, but I'm no longer concerned about that; I mainly just want to solve the "illegal operation" error. I haven't tried different memory yet, but I'm kinda doubtful that's the issue. Any other ideas?

back in the day i remember one system that showed really weird errors with 512mb running windows 98, i remember that downgrading to 256 solved the issue.
it was the memory upgrade on my athlon xp 2400 that had 256mb, my dad asked to his customer if he was okay if we swapped mine 256mb module with his 512mb and bam, i got more memory and the customer had a stable system.

GordonFreeman wrote:

I tried slowing down the CPU, and I tried editing Config.sys: neither of those things fixed the "illegal operation" error. I haven't tried running the Windows installer again, but I'm no longer concerned about that; I mainly just want to solve the "illegal operation" error. I haven't tried different memory yet, but I'm kinda doubtful that's the issue. Any other ideas?

Like legaCy says, remove some of your RAM. 512MB is technically the upper limit but it's good to eliminate one possible source.

I got the "Illegal operation" error a lot in my VM Windows 98 and I remembered spending a LONG time trying to fix it and there's a TON of possible reasons:

- bad RAM
- bad drive
- bad Windows installation / registry (caused by bad RAM or bad drive)
- CPU too fast
- any sort of reading error

Basically, it's such a general error that the only way to find the reason, is to have spare test to swap out. The RAM seems to be the easiest thing to try first.

I tried swapping the 512MB memory for 256MB. The memory works, but it didn't solve the problem.

What I think I should do now is to try removing the m3D so I can determine if that's a factor.

GordonFreeman wrote:

I tried swapping the 512MB memory for 256MB. The memory works, but it didn't solve the problem.

What I think I should do now is to try removing the m3D so I can determine if that's a factor.

Anything easy to remove is a good thing to try before you look further so yeah I'd do that as well. It could be something as simple as a bad driver too.

red_avatar wrote:

Anything easy to remove is a good thing to try before you look further so yeah I'd do that as well. It could be something as simple as a bad driver too.

I've tried multiple different drivers to no success, but I haven't tried all of them. One idea I had is that it could have something to do with the specific port I installed the m3D in. Maybe there's a conflict of some kind between it and my sound card due to how they're arranged. Still, it makes sense to just remove it first, that way I'll know if it has anything to do with the m3D at all.

So, I tried removing the m3D, and that made no difference. I think it's highly unlikely that the m3D is the cause. So I've now ruled out all of the main areas of interest. It can't be: the HDD, memory, OS installation, the m3D, or the CPU's speed. I've tried replacing/altering all of those to no effect, so there's no way any of those things are the cause. A new idea I have is that it could be one of the drivers I installed - so I could try reinstalling 98 again, and see if the problem is present before I install any drivers. Then, if the problem isn't present, I can install drivers one by one and do testing each time until the problem appears. I'm not sure how likely this is to be the cause, because I haven't installed any new drivers lately other than the m3D ones, and the problem never appeared until just recently - although I guess it's possible that it already had the problem, and I just didn't notice because I didn't do the thing that triggers it. Anyway, eliminating drivers as the cause is about the only idea I have left at this point. Is there anything else I can try? Failing that, I think the only other option would be to transfer parts from this system to another PC.

I also thought about installing Windows Me, but I'm doubtful that would make any difference.