Radeon 5970 prevents the computer from booting from the first time

One last question - is it safe to enable ASPM L1's and L0 in my BIOS or this card doesn't support it ?

Well, ASPM stands for Active State Power Management, so i wouldn't activate it. But that it just me :)

Can it hurt ?

No, but it will probably draw some power from the card when it is not in use, if your using a laptop this could help with battery life, but since your on a desktop, it won't have too much effect, a couple of bucks on your electric bill :)

But that's just me! if i were you, i'd run the PC a whole day with the ASPM on, and another day with ASPM off, if you see any noticeable differences, then choose the one that fits better into your likes

EDIT: btw, is the PC working fine now? with the new PSU...
EDIT #2: DOH! i just read last page where you said the PC is working just fine glad to hear we helped!

We can close this thread now! problem solved

Actually, I am not sure if it's solved completely. My video card is fine now, and it boots OK, but now the HDD fails the Seagate Tools for Windows Short DST self-test and mentions something about "electrical part" when I run the test under DOS. What's even more bizarre is that when I took it for repairs the technicians said they ran all the tests on it and it passed them fine.

I am totally puzzled.

Edit - yeah, you can say the original problem is gone, in a way.

Ok, i've been reading about this and it could be your hard drive is failing by now, it could be a collateral effect of the old PSU not been able to deliver enough power and probably it damaged the HDD.

Type CMD in your search bar, run as an administrator and type "chkdsk X:"

X is your HDD assigned letter, post a screenshot here with the results please :)

Here you go :)

Weird thing, not a single kb in bad sectors.. could you try to disconnect the HDD that's giving you the issue and plug it to another sata power connector on the PSU? just to discard that... and see if it's still giving you this DST Self Test Failure

Still no luck. Here is what SeaTools says.

Ok, Dellius, i've found some information on Seagate Forums, they say there that when a HDD is giving you a Short DST - Fail, it could be the hard drive failing

You can try a zero fill full with seatools. If that does not fix it then replace the unit.

Do you have a spare drive to backup your data? or you don't want to reinstall windows and see if that's the issue... not saying that windows is the issue, but the HDD!