My trial recently ran out and I've had PC problems since.. without it, cheers if anyone can help.

You can try this one

a lot of the files you can set windows to remove or use programmes like CCleaner

http://www.ccleaner.com/

some programmes (I'm not saying System Mechanic Professional 7 is one of them) find lots of problems and can fix them at a price, where as by looking around you may find freeware programmes will do similar things

firewalls and anti virus are both available free