[Baron Munchausen]

Yes, removing or disabling the fan is likely to cause problems. Those old power supplies may have had a bit less wattage but they definitely built up a lot of heat. It's dangerous to even open the power supply, actually. There are capacitors in their which hold very large charges for a long time.

There are 'special' power supplies available these days with very quiet fans if all you want is a lower noise level. I don't know if they are available for the old AT type systems, though. They might only be available for ATX systems. You'll have to do some Googling and see what turns up. Try searching for something like 'quiet power supply'...