Computer freezing then painfully slow

I was attempting to download a podcast on my Toshiba Satellite and was told i needed to update adobe....i think it was adobe, i wasn't paying much attention.
Following that the computer froze and could not be turned off unless i used the power button.
Then every time i turned it on it would be incredibly slow. Then when i attempted to press any button it would freeze.
I then disabled anything that wasn't essential at start up and this improved it slightly.
It will perform very basic functions but painfully slowly and many programs appear to much for it and it freezes.
It connects to the internet but Firefox soon stops responding.
One time it appeared to be working much better then crashed to blue screen.

It appears to work fine in safe mode.

Hope you can help.

stylustrouble