Random Logouts and System Errors...

My computer has driven me insane lately.
Every time I try to login, I have to keep trying over and over before it decides to let me login and then actually stay logged in.
Usually I start it up and notice it is extremely slow (like, it can take 20 seconds to close a window), and usually i can solve this by closing off the computer and restarting it - then I try to Login, and fail lots of times.
First I try to get a connection, but it says it can't get one, or it comes with some System Error warning.
I disconnect everything, and try again - it still fails.
I disconnect everything again, and then I MIGHT be allowed to Connect, but then it will randomly disconnect for no real reason.
I've checked the cables, and nothing is loose.

I reckon this is some sort of virus, but is there any easy way to solve this should there be some other explanation?
I'm using an Asus laptop connected to a pretty old Fujitsu Siemens (since my laptop's LCD screen is broken).

Go to task manager and close all programs that aren't SYSTEM, except for explorer.exe

Perhaps one program is interfering.