I have a IBM thinkcentre and it turns on but nothing is displayed on the monitor. I tried switching the RAM and found the RAM was good, but still nothing. when it starts up it beeps once, then three times, three more, one, then nothing. Any suggestions?

Built in video btw.

if I read your post correctly and the beep code is 1-3-3-1 then its possible that The error you are getting is that there is a failure while accessing, initializing or "autodetecting" the extended memory on your board.
The extended memory is all the memory installed beyond the first megabyte.
Possible causes:
a) defective memory module
b) defective motherboard
c) not well seated memory module
d) incompatible memory module installed (if you just did install one or some).
Normally, you can set your BIOS not to test that memory, but of course, this bypass will not fix the real problem. You will probably see a lot of blue screens then.

how do I set the bios to bypass it if i can't see anything on the screen? no bios or anything when it turns on. Monitor keeps flashing. But the beep is correct.

Right I see your point, wasnt thinking lol

the first thing I would do is to try to confirm that in fact it is a bad RAM module.

take all the RAM out and install just one, make sure it is well seated and turn the computer on and see if it boots, try it in all the slots, then do the same for all the RAM check them one at a time

if the computer still will not boot then its eaither a defective motherboard, or incompatible memory modules installed