A friend of mine recently picked up a Dell PowerEdge 2850 server for peanuts. You can find them well equipped on Ebay for chump change these days, and while they are a couple generations old now, they're still very powerful compared to desktop hardware for the same cost. Common configurations include a pair of dual core Xeons, 4 or 6 gigs of ram, hardware raid, dual gigabit nics, etc. Of course, my friend is a Windows user, and really wanted to run XP on it.
In their infinite wisdom, Dell provides drivers only for server variants of Windows, so getting things going isn't exactly straightforward. The issues are with the RAID controller and the Ethernet controllers. His used Intel ethernet, and they're mercifully friendly when it comes to drivers, but the RAID controller was a different story. The Dell PERC 4 card is actually a variant of LSI's Megaraid 320-2, but with different firmware and PCI IDs. Some forum threads found on Google seemed to indicate that the driver for that Megaraid unit would work, but after a long effort, Windows wasn't having it.
In the end, I ended up modifying the driver package Dell provides for Windows 2000, to allow installation in Windows XP. The driver has full functionality, as 2000 and XP drivers are more or less the same, but Dell was explicitly blocking XP installation. A few minutes in a text editor was all it took, and he was happily installing XP.
Given that there was a fair amount of discussion of people trying to make this work, and none of the info we found actually succeeded at making it work, I am reposting the modified drivers for anyone else who may be in this situation.
Instructions are simple. With XP, you have to load your drivers from a floppy disk during the installation process (you are prompted to hit F6 if you have drivers that need to be installed). Simply format a floppy with the FAT filesystem, and drop the contents of the modified package onto it. If prompted to choose your hardware from a list, it is the PERC 4E/DI .
After you have installed Windows, you will need to install the Intel drivers for the ethernet controller. His used the Intel 82541GI chip, the driver for which you can find here.
Your device manager will still show a few missing drivers, which we just ignored. You can't really do anything with the SCSI Backplane Controllers in XP anyway.
You can find my modified driver pack here. Please note that these are not supported by Dell or myself in any way. While they worked for my friend, they may cause something terrible to happen, like Gilmore Girls being brought back. Also, please note that I make no claim of ownership of these drivers, they are unchanged from the ones directly available fro Dell's support site other than the ability to install on Windows XP.
With that said, I hope you find this information useful, and I welcome your comments.