Help needed! Serious computer problem!

[grapefruit]

Update: Nevermind, I found what was causing the problem. 
It was a driver conflict between the new graphic card and the external soundcard. Booting into safe mode and removing all ATI drivers of the graphic card solved the problem. The external sound card still isn't reconised, but that's no big deal. I'm using the on-board one now, although it greatly cut off on sound quality. But it's okay, it's not like that computer can really support music-making software anymore anyway.

Still, again, a huge "thank you" to everyone who helped. I don't think I'd have had the patience to go through repairing this computer without your support. In the end, it cost me much more time and headache than money, so I guess it was worth it 

[Computer_Commando]

Update: Nevermind, I found what was causing the problem. 
It was a driver conflict between the new graphic card and the external soundcard.
...The external sound card still isn't reconised, but that's no big deal. I'm using the on-board one now...

Try the sound card in a different slot.  It sometimes resolves the conflicts.

[grapefruit]

Try the sound card in a different slot.  It sometimes resolves the conflicts.

Yeah I tried, but without success. I'll eventually do a huge clean up of old software and drivers then work my way from there to make both the graphic card and soundcard work together.

Also, I still do have some booting issues from time to time, but that seems to be caused by connections to the pci-e port. When that happens, just removing and reinserting the card solves all issues. Other than that, it works like brand new. No slowing down, no locking up, no glitch, no beeping alarm, no overheating. It is as stable as before, and a lot faster than it used to be (for example, just logging onto windows would require a good 15-20 minutes to load, now it barely takes 2 minutes at most.)

[grapefruit]

The locking up problem along with the long beep came back today...

Lowered CPU temp to 50-55C at most.
Power supply tested and supplying enough power.
Ram went through a few hours of memtest without any problem.
Graphic card brand new and installed properly.
Soundcard removed.
Hard drive tested, file system checked and fixed using chkdsk /f

What's been left untouched:
Motherboard
CPU
External network card (never been used)

I have no clue of what's going on this time. Could very well be related with the hardware issues described in the earlier post (which oddly reminds me of the old NES and SNES with the game cartridges that gotta be removed, cleaned, and reinserted a few times before it actually works...), but I don't know what I can do about it.