“Solid performer - not fast but very reliable”
I've had the IBM NetVista 6832 for many years now, which is based on the 1.3 GHz Intel Pentium IV. It was a good deal in its day, but is definately dated now... It came with the odd "RAMBUS" memory which is a bit of a concern when trying to find memory to upgrade (you have to use "blank" memory modules in unused slots for this memory). The system board uses Phoenix BIOS, and has onboard business audio, 2 IDE, 1 floppy, and 4 USB 1.0 slots, plus 4 PCI slots (1 is taken by ethernet adapter, 1 for modem)...plus one AGP video card. It came with a CD-ROM drive, which I've since replaced with a DVD burner. It also came with Windows ME, which I had lots of problems with (not specific to this PC) and later installed XP on it.
The system was good for its time, but of course now seems dated, but I still use it. It has been very reliable (especially compared to the laptops I've had, several IBM Thinkpad and my current HP DV6110US), the only repair I've had to do to it was to replace the NVRAM battery supporting the Time-of-Day function (which stopped working when the battery died...$3.20 for a replacement battery and it is back in business.
The case isn't particularly space-efficient, only has provisions for one hard disk...I modified the bracket for the drive to allow 2 drives to be mounted (there is plenty of space available), but it would seem that this would have been accomodated from the stock offering.
The system came with a "fancy" USB keyboard (with lots of programmable buttons for user functions, I played with them when I got the system but have since forgotten about them) and a USB Mouse...I think it came with a 200 MB hard disk, which I've since replaced with a larger capacity (and higher RPM) one.
If you need a stable, but not necessarily fast system, this would be hard one to beat.