Random BSODs Caused by Random Files with Differing Stop Codes

Since 16 Feb 2013 to today 22 Feb 2013 I've been getting Blue Screens; these appear to be completely random each time with different stop codes and (according to Blue Screen Veiw) are caused by different files. For example;

Caused by ntkrnlpa.exe or atikmdag.exe, or ks,sys, or USBPORT.SYS, or dxgkrnl.sys, or dxgmms1.sys.
At times I'm unable to do anything on the my PC as these are known to happen before Windows logs me in.
Attached the Blue Screen View records of the BSODs (trying to figure out how to open .dmp) up to 21 Feb 2013. Most recently it was the ks.sys that caused the BSOD but no file was created nor does it appear in Blue Screen View. I know what these files are rooted to but neither Windows Update nor any driver update has solved the issue hence my post here.

Activity on the PC doesn't seem to be a factor as the BSODs have occurred while I've been playing games, watching DVDs, listening to MP3s, browsing the web, editing pictures on the PC... I can do anything and at some point a BSOD is guaranteed to happen. They also occur randomly, as yesterday (21 Feb 2013) I was able to play games until 23:00 and then I was unable to log back into Windows because of back to back BSODs while the day before I was unable to do much because of the frequency of the BSODs.

I've installed and re-installed a dozen times over and run the updates and done disk scans and defrags and virus scans and run Windows System Repair and nothing has helped. I'm at my wits end here and don't know what else to do. I suspect it could be hardware faults as my PC is at least 7 years old.

If you performed the above task then my guess is it may be hardware related, When you mentioned Re-installed are you refering to the operating system? If so have you deleted the old Partition and recreated a new one prior to installing windows?

Do what northernsoul suggested, that way he can get a better idea as to what's causing your BSOD

Configured Windows, can't run spec tool because I can't download .NET Framework on my 2MB/s ADSL line because ISP is throttling to below 56k speeds. Blue Screens have been preventing me from posting further. Memtests and driver checks as well as system scans all check out fine.