This is king of weird. I have 5 MVP3 boards and none display issues similar to what you are getting. Try older nvidia drivers (especially since 3D Acceleration works on the Radeon). As old as possible. I got black screen and display corruption on a Pentium 3 using Forceware 7x.xx drivers, but everything works great with 4x.xx drivers.

If using early drivers doesn't work I'd say try swapping ram and try using another CPU. If that doesn't work either, the board is probably dying.

Ok, so i did the following:

-Replaced CPU to K6-2 300 (officially supported by mainboard)
and set the 66 FSB
-Installed 2 double-sided SDRAM modules
-Reset BIOS settings
-Format CF card and put fresh installation files
-Install Win 98 SE
-Install unofficial SP2
-Install DX 8.1
-Install Forceware 44.03 (no luck - system freezes/restarts just before Windows GUI loads)
-uninstalled driver
-installed Via4in1
-installed Forceware 28.x (no luck, same issue)
-tried old Detonator drivers (no luck)
-disabled DMA mode in hard drive (no luck)
-changed clock source (with jumper) to AGP (no luck)

then I installed Omega Drivers 14.523... it seems to work 😜 i tried Riva TNT2 PCI and Jazz Jackrabbit 2 works without image corruption, i need to test 3dmark2001 and Half-Life now...
before that I thought that there may be a problem with insufficient power in the slots, so I could solder some wires to traces on graphic card and plug that into molex, but let's check if 3D performs good now.

Update: And it started bencharking! now it's time to do some stability tests, i hope that everything will work. Thanks for the advice about drivers. But none of official Nvidia drivers worked, only these alternative seem to be okay.

Glad it seems to be working. On my MVP3 board, there is a BIOS setting called "Write Cache Pipeline." I had problems with graphics cards and general instability when this setting was enabled. Apparently, WCP doesn't play well with AMD CPUs. Maybe your MVP chipset has the same issue.

Try Forceware 41.09. That's what I use on my MVP3 boards for Nvidia cards. They work with cards up to the FX series, and I've had no issues with them. Also, I'd stay away from the Unofficial Service pack. I've had issues with it and socket 7 machines and slot 1 machines in the past.

All right, I had some problems, but now everything is almost OK. After I had success with Omega drivers I installed K6-2 533 CPU again. And screen was distorted, like it was before. So i tried K6-2 500 and almost all of distortion was gone, but there was still some. Then I tried K6-2 350 and everything was working fine, just like with the K6-2 300...

I looked into the manual, and there was a table with jumper settings for the CPUs. Fastest processors were K6-2 450 and K6-III 400. I did some research, and it looks like K6's faster than 300 MHz have Chomper Extended (CXT) core, which has some different features. I think that this motherboard couldn't recognize properly 500 and 533 processors and it may have treated them like overclocked K6s with regular Chomper core, and it caused problems.
I upgraded the 300 to 350 with CXT core and it works perfectly fine, because it has official support. Well, i think I should buy K6-2 450 then, it should be compatible and it only costs peanuts. I could also look for the BIOS update, but it already has a date of 01/03/2000, so maybe it was never intended to support these CPUs.

I also had a problem with ISA sound cards (tried ESS 1878 and CT AWE 64), sound was a bit distorted and lagging. But when I removed PCI TNT2 graphics and installed AGP GF3 Ti200, everything sounded clear. I will replace that later with AGP TNT2 or AGP GF2MX (because GF3 will be a waste of both processing and electric/thermal power - and this board surely wasn't designed to support power-hungry video cards). This mainboard has a PCI-ISA bridge, so I guess that PCI video card has taken nearly all the bandwidth and there wasn't much left for sound card (PCI latency patch didn't help). But I hope that Voodoo 1 in PCI slot won't be a problem for the sound card, i want to use it along with TNT2 or GF2.

//update: Some sources say that my version of BIOS should support K6 500/550, but maybe it wasn't fully tested by the manufacturer. I'm going to buy the K6-2 450 and test it anyway.