If it has a single 867MHz processor, it's probably a
QuickSilver.
It has an older P-ATA controller, and I'm pretty sure that, without modification, it wil not support drives larger than 120GB. There is a software hack floating around that's one option to get larger PATA drives; the better option is to get a SATA controller like the one discussed here:
http://www.xlr8yourmac.com/feedback/Macsense_SUA-100E_card.html
Once you go to SATA, there isn't any real limitation in what you can use, so you can use the 500-750GB SATA drives.
This might be helpful, assuming you are able to read French:
http://forum.macbidouille.com/index.php?showtopic=193899
Finally, you are probably going to want to budget to get Panther or Tiger for it, as well as some memory -- probably adding 1GB would be grand, although you can probably live with adding 512MB. The OS upgrade is really worth it, I think, in terms of improved serving functionality and stability. You really do not want to be on 10.1. In fact, install Linux if you need to, but don't use 10.1....
Budgetary considerations:
- Copy of Tiger -- probably about $50
- 1GB memory - 2x PC133 SIMMs - $108 (according to Dealram.com)
- SATA controller -- seems that, if you shop around, maybe as little as $80, up to about $250.
- Hard drives -- depends on what you want