!RAM problem AND a separate HD question!

[sixbynine]

(crossposted to another forum website)
Long, detailed. Thanking everyone beforehand :D Okay.
Assembled my system early this year, circa March. Ran fine until I got BSOD last week, something mentioning IRQ. I turn the PC off, back on, and get the speaker error System failed due to overclocking. I call the only person that had ever used my PC recently, and found out my cousin had it overclocked 30 percent since a few months ago (to 3.6Ghz)
I bought a new similar mobo, still didn't work. Took out the CMOS battery, replaced, same problem. I take out one stick of RAM and now it works - I put the stick back in, it won't work. Problem is, I don't have a detailed record of what kind of stick I bought, all the label says is
Komusa-PC3200 512MB DDR. Each stick (four total) has copper heatsink-type plating, or at least something resembling it if not plating. Can I buy another single stick? Does anyone know of a site that sells the exact kind I'm referring to? :)
Secondly, I have my same ASUS P4C800 deluxe motherboard. The specs on the box say Multi-RAID for ATA133 & serial ata.
I have this HD right now :
http://seagate.com/cda/products/discsales/marketing/detail/0,1081,597,00.html
ST3200822A, Barracuda 7200.7 Plus-200GB Ultra ATA/100, 7200 RPM, 8.5 ms avg.
Could I buy another identical HD, set it as a slave, and have it work? There's another empty connector at the end of the cable the current HD is on, and I have a 430 watt power supply.
Thank you. :) [again.]
Feel free to AIM or email me if you have knowledge on this subject.

 

[Big B]

I've never heard of the Komusa brand, so I can't say what memory it uses. What you can try is get Memtest 86 and put it on a floppy or get the .iso file and burn it to CD---which you can boot off.

As for running RAID, that depends on the ability of the Promise ATA/SATA controller. Even if it does work, you've got a few things that might not make it worthwhile. First, the ATA/IDE standard limits access of 1 drive per channel at any given time. Yes, you can probably have two hard drives on the Promise ATA controller (this function will not work on the other two ATA connectors powered off the ICH5R southbridge on the motherboard), but if you're hoping to run them in RAID, you're going to be sorely disappointed in the performance. 2ndly, running them in RAID 0 will require you to reinstall your OS, providing that the controller supports this in the first place. The reason behind this is that the hard drives need to be made to be viewed as an array, and due to the way RAID 0 works, it will destroy the data in order to do this process.
It might work running RAID 1, if you set it up to mirror your current disk and not vise versa---but back up just in case if you decide to try it.