Windows XP forum: XP won't boot

I have an old (10 years?) Compaq Deskpro EN, which one day when I was online, shut down. When I tried to restart, nothing happened, just a black screen with a blinking dash mark in the upper left hand corner. A friend of mine gave me this computer with XP professional already installed. I don't have the installation CD or the bootdisk cd, so the good folks at CyberTech help forum walked me through the process of burning a restore disk online. When I inserted the disk, I actually did get something other than a blank screen. Sometimes I'm able to get to the Windows Setup screen, and sometimes not. When I do get to the setup screen, I'm asked if I want to install XP (which I don't because I'm hoping to retrieve files), or repair an existing installation. When I choose repair, sometimes I can get to the recovery console. When able to do this, I'm asked which system I'd like to log onto. Since there's only one option, I choose 1, then enter. From there, I type in the command prompt chkdsk. At this point I get a series of error messages, it seems a different one each time I try:

STOP: c0000139 (entry point not found) The procedure entry point NtSerialize Boot could not be located in the dymanic.link library ntdll.dll

file\i386\ntkrnlm[.exe could not be loaded
The error code is 7

file setupdd.sys could not be loaded
The error code is 7

STOP: c0000221 UnKnown Hard Error
\systemRoot\system32\ntdll.dll

Anyone dealt with this before? The moderator from CyberTech lives in Germany, and with the time difference, we've been going back and forth for a week, with no progress. I thought I'd give Cnet a try. Also, I can't access BIOS (del I think) or safemode (F8?). When I tap these keys, I just get a beeping noise from the tower. Any help would be greatly appreciated.