From the manual download @ HP xw8200 Workstation*-* Manuals (guides, supplements, addendums, etc) - HP Business Support Center Light flashes red 5 times then pauses 2 seconds then has 5 beeps says that your memory modules need to be checked and or replaced or that your motherboard has gone out...
I would opt for the memory modules to be bad.
Remove all power sources and external cables/connections
Open side panel
ground yourself to the unfinished frame of the computer case.
Look for the memory modules...usually long slim circuit boards inserted into sockets toward the back of the motherboard behind the CPU/fan/heatsink.
To remove ...there are locks on each end...press down on the lock tabs and the boards should raise up. Remove the boards and wipe the connectors with a clean cloth being careful not to snag on the connectors. Replace the boards and restart you computer.
If that doesn't fix the problem then remove each card and try to start the computer with only one stick in position. Still doesn't work...switch the removed ram modules...and try again.
If it works then you need to replace the removed module with a like type...you donot need to increase the ram amount as xp is about limited to the 3 gigs that you have installed.
Hope this helps you out.