About the Memtest, I saw the same screen all the time. Some count were going at over one million, but I couldn't figure out was it about errors or something else...
You were seeing this, right:http://www.memtest.org/pics/amd64-big.gif
As long as the amount of 'Errors' (a little to the bottom-right) is 0 for all the listed tests done.
If you want to, you can run it another time, but as it conflicted pretty much with your system last time I do not really recommend it.
Anyway, my Firefox crashed only once yesterday. Just a few minutes ago my pc almost tilted while copy-pasteing a picture. The system shut down explorer.exe and drwtsn32.exe.. for a while only, I guess, cause the system didn't restart, and now the processes seem to be working again.
Yes, drwtsn32.exe is the program which tries to find out what was wrong (never helpful really) and explorer.exe is sometimes shut down when it is really difficult/hard to close something, for instance Windows Explorer when it has crashed.
These two have been the only problems I have had since Memtest yesterday morning. Right now, and usually, I have Firefox, Adobe Photoshop, notepad, Windows Media player and Live messenger open at the same time.
The problems you have are a little difficult to categorize. It may very well be because you are just running a lot of programs at the same time. When I do that pictures also load slow when copy-pasting. For example, Adobe Photoshop is not a light program and Windows Live Messenger can also be pretty irritating nowadays.
This may be an interesting page to work through, as it lists general cleanup tips that could really help speed up your computer and make it crash less:http://www.malwareremoval.com/tutorials ... slowly.php
Please let me know if you have had any problems since your last post and if you consider this case nearly done.