My friends Evo D510 failed to boot with a classic mup.sys file corrupt error and since he couldn't get the repair cd working (CD-ROM error) he got the HDD out and tried replacing mup.sys in another PC.

The real problem occurred when he tried to replace the HDD and re-boot. The system hanged even before the monitor switched on and after a short alert sound six beeps were emitted. Tried re-slotting RAM removing USB devices etc. but nothing works. It's only beeps - power light comes on and after the beeps CD tray pops out.

I've consulted the manuals and found that six beeps stand for BIOS corrupt. But could it really be the case? Would clearing CMOS work or is there another procedure? Me and my friend have never reflashed BIOS in a non - working computer and Compaq website is unclear about it too.

What's the best way to go about it? Thanks in advance for reading and replying.

Hi,
Do you know the version of the BIOS that was on the computer?
If so, go to the Compaq site, and you can possibly download the same version.
If you don't know the version, then it's really a chance that you will download the correct one; even an upgrade.
I suggest taking it to a local computer repair/sales store; let them fix it.
Best wishes,
fredg

Just one good general advice: do not flash a BIOS that is not properly running. The flashing will most probably fail, and ruin the MB.
Specifically, for your problem: your problem began when installing a new hard drive. It is almost impossible to damage a BIOS that way. So you should not really think of flashing the BIOS anyway.
Try zeroing the BIOS settings instead. (there should be a jumper on the MB for this). After that, you will have to do the BIOS setup of course. The procedure is in your manual.
While the 'puter is open, check if all cables are well seated.
And, what often happens when one replaces a hard drive, is that he ends up with conflicts in the drives' master/slave jumpering. Check that too:
IDE 0 Master: Boot disk (harddrive C)
IDE 0 Slave: spare for additional device (DVD drive, harddisk, CD drive)
IDE 1 Master: spare for additional device (if you have a CD burner, put it here)
IDE 1 Slave: spare for additional drive (extra harddisk, CD drive)
Second rule: you must NOT have only a Slave drive on an IDE interface.
Plugging sequence: IDE 0 master, IDE 1 master, IDE 0 slave, IDE 1 slave.