20 gigs to big

Hi,
The older Mother Board as in a 133cpu would probably not recognise a 20 gig HD. Most older MB's do not recognise over 4 or 8 gig HD's.
Mostly the 500 CPU pc's MB's will recognise a 20 gig HD.
A system with 32 megs RAM would work although with RAM so cheap I would go with 128 megs RAM.
A 20 gig HD uses little or no more power than A 1 gig and therefore the Power Supply need only be standard. The large draws on the PS are the optical drives, ie; CD ROM, DVD and espically the CD-RW and DVD-RW.
USB devices use alot depending on the device.
If you are going to run say an AMD 2500XP with a CD-RW and a DVD-RW and a CD read and a floppy and a G-force video with a maximum sound card and a RAID card then you will need a 500 watt PS.
However a standard 250 to 350 watt PS on an AMD K6-550 with a CD-RW, 8meg Video card, floppy, and a more standard grade sound card then you will be fine.
I do hope this helps,
fred

Most of what you want is covered in the first answer. The biggest concern will be the operating system you will be using to access the system.

Most Pentiums ove 100 mhz will recognise HDDs up to 20gb not problem, NB most not all.

However at that speed you can run into operating system problems as the CPU will not run WinXP, Win2K becomes a dicky proposition, thus you will likely be running Win98 and only read FAT32/16. If it is NTFS you can have some problems.

If the system BIOS recognises the drive properly but you cant read it due to the files system or trouble recognising partition size, you could try loading the 20GB as a second HDD and load a smaller one for the OS with one of the latest Linux versions and one of the Windows reading programs.