Lots of times when I get on my computer and I try to open a page it will go very slow and it will either (if I'm lucky) go right to the page or say it can't find the server. Then I've been signed out for no reason and had a message to pop up saying you were signed out because you have signed into a different computer wich makes no sense to me cause I was on the same computer. I've dne virus scans and it shows nothing and the alert will say something's wrong but then it will flash to okay before I can find out what it was. But the computer will still act up. Its not as bad on upstairs computer. And sometimes something pops up that says "something or other exe. is attempting to access the internet this could be a potential hazard." what does this mean?

The "XYZ is trying to access the internet" part is your firewall (or some other protection) warning you that something is trying to access the internet. It could be a valid piece of software trying to access the internet or it could be some malware trying to send information to/from you PC. If one of these prompts come up and you don't know what the program is - it's always best to click no.

First thing I would do is to run some spyware scanners on your PC. There's a few links in my signature. Run these in safe mode for better results (reboot PC, hold down F8 as it boots, when prompted choose Safe Mode). Do the same on the upstairs PC too - just to make sure.