OK, I see this is for your Daddy, so I'll skip the kiddy cases and recommend one of the nice black Inwin or Enlight cases from Newegg. Cost: ~$60
The power supply with those cases is good enough, but if you want something better, you can go "overkill" with the Fortron - FSP400PFN 400W Power Supply. Cost: ~$60
Next, since I doubt he has a gigabit network, I'll recommend the Abit IC7 motherboard. Cost: ~$145
You'll want a couple 256MB Corsair XMS PC3200 modules. Cost: ~$120 for two
Now, you'll want decent video, even if the system only plays games once in a great many moons. The Radeon 9600 Pro is a good solution. Cost: ~$180
You need a DVD-ROM. The Light-On LTD-166S is good at both DVD playback and CD ripping. Available in Black. Cost: ~$40
You'll want to write CD's, you can find a great deal with the Lite-On LTR-52246, available in Black. Cost: ~$45
Of course you need a hard drive! The Western Digital WD1200JB offers great performance and a 3 year warranty. Cost: $125
Of course you'll need a processor for all of this! The "sweetspot" seems to be the Pentium 4 2.6GHz 400MHz (Retail Box). Cost: ~$200.
Now, you'll probably want a floppy. It really doesn't matter what you do there. I'd pick up a used one for $5 in your situation (I get mine for free), but if you want a new one: Cost: $20
As for monitor/printer/keyboard/mouse, you should pick those out after trying some at a store.
Add those up for me and see what a bargain you get, in a top quality system!
<font color=blue>Watts mean squat if you don't have quality!</font color=blue>