XxNiXxX... what do you mean
"the computer has no info on it"?..
Did you access the BIOS setup menu?
It is rare (these days) for a BIOs to not report the make and model of a hard drive.
Go to the following URL, Download the free Ada32 system information utility...run it and that will tell you the name, make and model of the drive (unless, Compaq had the drive made especially for them..which only adds Compaq's data to the stored data on the ROM chips data base and not the HDD's manufacturer...worth a shot).
http://www.aida32.hu/aida32.php (simular to Sisoft Sandra but better accuracy).