So I have a "vintage" gaming rig if you've followed my post, and I've got a few questions about it, the specs of the PC in question are:

First and foremost, I only have $25 or so in the whole computer. I don't intend to spend a lot on it either.

Windows 98 SE Plus!
MSI Socket 478 SiS chipset mATX motherboard
Celeron D 3.06GHz
1GB DDR400
AGP 8X nVidia GeForce FX 5500 256MB GPU
Sound Blaster Live! Value PCI sound CARD
2x 80GB IDE HDD's (WESTERN digital and a seagate I think, I've forgotten) For windows 98
1x 160GB (Or 320GB, I've also forgotten) IDE HDD for Windows XP

With that out of the way, I'll cut to the chase, first question:

First, does anyone know of any "QUIET" Socket 478 CPU coolers? Even with the fan controlled to spin down and SET to let the system run a bit on the warm side, it's still loud! It sounds like a face hugger is stuck in a vacuum when my CPU fan spools up under load. If nothing else, I guess I'll have go go with a Noctua "I've spilled brown on my fan" 60mm CPU fan, they seem quiet enough. But $15 for a fan? Bah, this really offends me.

Second, does anyone know any alternatives to mechanical hard drives I can use on the IDE bus? I know CompactFlash is one option, but a bit pricey. SD would probably be laughably slow and ultimately not survive long term use. Sooo, I guess if anyone knows anything other than CF I can use, lemme know... Unless you have a magic trick to make SATA work on Windows 98 'cause the SiS chipset on my board does not like Windows 98 at all!

If you tell me "Emulation is a better solution", I'll completely ignore you. Emulation bores me, real hardware amuses me, even if it's a bit too new it's still great playing games from my childhood on a CRT. I however, do not miss trackball mice... Not at all... 

Otherwise, if you have suggestions to make the CPU cooler quieter, or storage options let me know! Hi

You can still get new socket 478 fans for under $10.00. Ebay would be a start or a local computer shop could have old stock. If you under clock your CPU  you may be able to slow the fan with a fan controller  and still keep temps low. Have you tried lubricating the fan like in this video https://www.youtube.com/watch?v=j6yb4sGg_FY

You can get IDE to SATA adapters like this one  https://www.amazon.com/dp/B0096BEJDI/ref=psdc_3015394011_t1_B001PYSAJI this supports boot from any windows version supported by the IDE interface.

I would check your chipset is not limited to hard drives 160 GB or less. Before installing other drives.
You could use  a PCI sata card like this one https://www.amazon.com/GODSHARK-Controller-Internal-Expansion-Converter/dp/B07R3YFFR7
Which will boot windows XP but not windows 98 so you would need an IDE drive for 98.