Seamingly Random Hangs

I have this extremely irritating problem for quite some time now and I hope some of you proper geeks can help me find a solution! It's a kind of a mixed issue, i don't know if its software or hardware :/

So the computer hangs, I cant use keyboard or mouse or anything, peripherals completely unresponsive (num lock/*lock lights dont switch on kbd). I have no Idea what is causing it but during months of testing Ive come to some conclusions: It seems its not a particular piece of software, PC sometimes hangs in safemode, might hand during logoff, hanged after intentional complete format and reinstall (software/hardware details at the end of the post).
There are two ways it happens lately the first is it hangs and doesnt unlock, 99% of the times it happens while playing a game, happens in StarCraft, happened in Crysis demo. I have to manually restart the computer from the button. (while locked, the red diode thingy doesn't blink at all) And a second type of lock, most often while on Desktop. It hangs for (i clocked it) exactly 13 seconds or a bit more, then unhangs, can hang again in 2 seconds or a while later but its never once per session sometimes it happens for 3-4 times. Ive noticed it does it either at random or while a program is being started/closed/restored from systray or taskbar. Lately it happens A LOT while trying to burn a CD or DVD, no matter size or speed. Also when inserting a disk it hangs for about 4 times.
The whole doesnt happen that often, sometimes it doesnt happen in an entire session. It has never happened if the PC is untouched, I had left it for 2 days and it hadnt hanged during that period. I dont appear to have heat problems while it was doing it more often in the summer.

My computer is about 3 years old now, it does this for at least 6-7 months or more.
Windows XP Pro
AMD Athlon XP 2700+
4x256 MB Ram DDR
geForce 6600 GT 128/128 AGP
MB is Asus A something with 88ts or something, Ill have to restart to see for sure
Seagate 80GB ATA (with those default conector thingys)
A newer Seagate 250GB (with a special cable, not the default wide one that connect the other drive and the disk drives)
Sony DVD Rom
New LG DVD RAM Drive

I hope you can think of something!

Btw, last week or so I get "failed to write to G:/ (newer Seagate) data lost" the popular windows error that I couldnt fix with that cache setting for the drive, and I dont think its the 40/80 pin cable issue because Its just now that I get that error.
Im ready for any instructions regarding gathering of further info y'all might need!

 

It sounds to me that it's either a RAM problem, or a possible IDE or SATA controller problem. Testing your RAM is easy enough: download one of the memory testing programs from the Memory section here at MajorGeeks. Be sure to the extended or advanced tests, and run at least 3 or 4 passes. All the testing apps are different, so if it doesn't have 'passes' or 'advanced/extended' tests, just let it run for at least 2 hours, preferably longer. Download and run the diagnostic tool for your hard drive(s). They're free at the drive manufacturer's web site, or here at Major Geeks in the Drive Utilities section. The HD diagnostics usually include a test for the controller also. Be sure to choose the extended or advanced tests for the drives too. It's probably a good idea to go thru the PC and make sure it's clean of dust and debris, and check all the cables and connections for good, solid connections. Maybe replace the data cables for the HD's... they're cheap. Also, check your power supply; be sure it has adequate wattage and amperage output for your system...

 

The PSU is 400 Watts, I've checked and cleaned the case often and I made sure its not physical. Im on to the tests now, never did a drive's test but ive done memory tests before and I had no problems. I shall see.. Thanks!

 

Could this be caused by an over-heating problem?

 

Well no, i've looked closely into that, my temperatures are within normal values. right now Its about 10C outside, the room is not heated and it hanged 5 times while burning the 300kb windiag.iso :< (i monitor with speedfan for mobo/cpu/hds and rivatools for the VGA)
What disk checking utility should I use? Im giving SeaTools a try now, but it displays an "unhandled exception error" and my second drive is grayed out and I cant test it, testing my 250' now (long DST).

 

Win' Diagnostigs test (did a boot CD) did 3 passes of extended tests everything passed, maybe ill do a memtest too. Im still bafled what to test the drives with rolleyes

 

A PC I built started doing that and I found out it was the onboard USB, it was one of the cheap ALI, or something brands. I disabled onboard USB and installed a NEC PCI card. I don't have the random hang-ups anymore. But it was just like yours, it would hang any time & lock solid - no KB - nada, would just repower to get going again.

 

But can such USB fail just like that? Ive been using all ports and no problems at all.
Btw the motherboard model is A7V880.
I made a memtest boo tcd I'll try it later today, yesterday with the win diagnostics thingy-memory-test At 2nd pass MATS+ test with cache off I got incredibly sluggish responses (of the satus bars, updating dead-slow, didnt keep the pattern of slowing completion times as the previous tests) I didnt see if it had errors on that test I.. fell asleep and the log file after X-ing the test was zero bytes :yum

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An interesting part is that I had my computer upgraded through the years, first it was an extra two 256mb ram, next year switching from ATi 9550 128/128 to the nVidia, and last year adding the new Seagate. Although it may just be general system fatigue Im almost certain it started doing it (noticeable often) after putting the new HDD. :confused

 

!!! It's a 100 % Disk problem, the new 250GB Seagate. I got so pissed I pulled the plug opened the case and ripped (gently ofc) the cables off it, now I do all the operations that caused the hangs and it doesnt happen!I went this far because it started hanging while I tryed the Properties > Tools > Error-Chacking option on the drive, just went crazy. So how can it be fixed? I have some data there that its hard to recover for the sole reason that its a lot.. I use to run some apps from the drive like ff, utorrent and winamp, i'll move them to the solid drive and see but i dont think it will help mainly because the system will still require a lot of reads from the drive (playing games or manipulating videos) The data cable thatconects the drive has a "Serial ATA" label, and on the harddrive ST3250620AS. What should I do?