[SOLVED] Programs having trouble starting up

On a laptop I'm using, I got a notification that there was a virus. Ran Malwarebytes and then Spybot S&D afterwards for good measure. Everything appeared to be in order. I then rebooted. After rebooting however, clicking on any program brought me to the "What program would you like to use to run this file?" screen. I mean everything. Notepad, Firefox, games, ect. I just tried to start everything to see if anything would start. Eventually I found that selecting the program I was trying to run from the "How would you like to run" menu would sometimes get it to work, but I'd have to do this each time I wanted to open something.

Example-
1. Click Firefox.
2. "What program would you like to use to run this file?"
3. Select Firefox from Program Files> Mozilla Firefox through the browse to select program.
4. It would open, take a long time to load the home page, then try to get me to reinstall firefox. If I did try, it would automatically just die off. No error message, updates, anything. Screen for installation would appear, then shut off.

Normally I'd just back up my important files and reboot, but... can't find the installation discs. So please, if anyone has any idea what this nonsense is and how to fix it, post here or send me a message. Currently using my desktop until then.

System in question--
Dell laptop, Inspirion E1505
Windows XP, fairly sure its the latest service pack. (Updated last night, shut off, then this started as soon as I turned it on today.)
BIOs flashing impossible, the girl who gave it to me lost the battery.