CF adapts directly to IDE and will max out your bus and exponentially decrease random access time. Hard drive benchmarks are disappearing because they all eventually fail and can be replaced by flash technologies. Cheat with modern tech, because nobody cherished the days of waiting for the PC to finish a storage task.

It's not that the current hard drive is slow, it works fine, but I can hear it crunching along, and for some reason, it decides to spin-up again after every reboot, which increases the start-up time by about 3-4 seconds.

I know all the benefits of CF, but a 40GB CompactFlash card isn't exactly cheap, the most affordable ones for me are 16GB at most.
Same goes for IDE SSD's, extremely expensive.

There must be another way, surely?

Not sure what you mean by "extreme."
800x 32GB CF is ~$1/GB
64GB M2 and an IDE to M2 adapter is around $80.
The IDE drives of those sizes back then were way more expensive than that.

Can't find IDE to M2 adapters here in Poland, didn't even know they exist!

Cheapest new 800x 32GB CF is ~49 USD here, that's too much, considering I've already overpriced on parts for upgrading the ThinkPad. We don't earn much money here.

If you're benching a conventional hard drive with CDM, you must run it on an empty drive for it to report correct scores. A non-empty drive will place the benchmark file somewhere other than at the beginning of the disk, where (in HDDs) the data rates are the fastest. This is one of the failings of CDM, which the developer does acknowledge in its documentation.

You should also mention the exact model of your HDD. Your 4K random results seem fast for a laptop HDD of the period... I wonder which one it is. I bet it's a 7200 RPM one.

Storage is faster so long as you don't use it?

Well, I'd rather test on a populated hard drive to reflect more realistic speeds.

The model of the hard drive is the: HTS548040M9AT00, with this Firmware: MG2OA5EA, running at Ultra DMA-5. It's 5400 RPM.
It has a very strange sticker, not the regular one.

The scores were made after a slim install of 98SE with minimal drivers.

You can also get IDE to SD card converters, and a SD card around 40GB would be dirt cheep.

Auzner touched on the main problem with CF and SD cards. The sequential speed is amazing, Random read/write much slower.
This isn't a problem with old PC's with slow ATA speeds and even slower HDD's. The increased speed makes up for this.

The newer the system the more likely you'll notice a slow down, Windows multitasking doesn't help reading and writing data off the HDD a lot more then DOS.

Not saying its a bad idea, Plenty of people have moved over to CF/SD cards fine and I can see this making more sense on a laptop than a PC where space is limited and they get bumped round a lot more. Just don't expect amazing SSD speeds from them