Blue Screen Of Death and Restart Help

Hello, I have a recurring problem that I have been experiencing for close to 2 months now.

I have a Dell dimension desktop with Sempron processor, I am running Win Xp home edition Service pack 2, and I have owned this machine for about 3 years. Lately I have seen the Blue Screen of death on too many occasions. I first noticed it with a series of restarts after our power had went out one night. So I started up the computer as usual and, when it got to loading my account, it restarted with the BSOD. It restarted too fast for me to get any information off of it, so I restarted, it stayed on long enough for me to disable automatic restart after the error, and I was able to copy down the error message, which I will detail below. I went through a restart loop a few times before, for whatever reason, it restarted normally and I did not have the problem for a few weeks.

Recently I got a new 3 in 1 Dell Scanner V305. This scanner is imperative for what I do. I hooked it up and put the installation and drivers disk in. I went properly up to about 97% complete, and when it said "installing new hardware" BSOD and restart. I tied a few more times with no better results, so i restarted in safe mode and then installed there. it worked but I got a bunch of "Runtime has requested the operation to terminate in an unusual way" errors I kept hitting ok and it installed fine. I restarted in normal mode and the scanner worked well. I knew I still had a problem, but I didn't know what to do.

So just today my fiancee tries to upload some pictures from our digital camera onto my loved but defective machine. When it was recognizing the hardware, it restarted, she says without the BSOD.

And it will do the same any time new hardware is to be installed.

Now, here is some background. About 2 years ago my internet stopped working. Turns out my Ethernet card was screwed up but I was in no position at that time to fix it. So, while moving, I store it at a friends house. Upon recovering it, i take a look into its guts to see what i can figure out, and I notice....my RAM is gone.....So a friend and I go out and buy some. we stick it in. I do not use my computer for a few months because of various life reasons, but finally we move, again, ad I get it hooked up. I noticed the first few time that it wouldn't turn on right. i would tun it on but the light would stay yellow as if it were hibernating. After a while it turned on and after a few more times I haven't had that problem.

Now for internet we got a USB Fast ethernet Adapter and hooked it up to my computer. we were going to go for a new ethernet card install but they didn't have the right size. the adapter worked fine though and we hooked it up.

Now that was close to a few months ago and I had noticed the BSOD just a week before that.

Now, I have done my share of investigating online and have isolated my problem to one of these:
A problem with RAM- Well having to get new RAM makes it seem likely. And I get the warning "Your virtual memory is too low, windows is increasing the size of your memory paging file" at least every other day.

New hardware installation- In addition to the Ethernet USB adapter I have installed various hardware since hooking the computer back up. One of these is a Philips USB game controller and I noticed the BSOD shortly after that.
The others are:
Cable Modem
Belkin Wireless Internet Router
A new Mouse
Sorta old but new keyboard
And the 3 in 1 scanner

Bad or corrupt Driver- This is possible. I have software that searches for the newest updates to all my drivers, and if I chose, downloads and installs them (Acquired after the BSOD started happening). But it is still possible.

Of course it could be anything else I may have overlooked. I hope I have been thorough in my information and, if not, just ask what you need. But I REALLY need help. I don't want to sound desperate, but I am at my wits end. This computer is vital for supporting my family and I want it running smooth. I know a decent amount about computers (more software then hardware) but I am no guru. an, hopefully, I'll learn some new things while you guys help me.

Lastly here is the dreaded BSOD error message its self.

Stop:0x0000007e (0x000000s, 0x00000000,0xf78DE7co, 0xF78DE4BC)

I was in a hurry to take it down and had trouble reading my own writing but I hope it is accurate and helps.

Lastly, I do not have my original Windows XP disk. So I won't be able to do anything with that, but I have borrowed one that I may try to use.

Thank you for your time and help in advance.