Can I install MSE to clean up my already-infected computer?
Q: My computer came with an anti-virus application preinstalled but the free trial period already expired. I haven't had an anti-virus application installed for ages. Can I install MSE to clean up my already-infected computer?
A: Speaking from experience, it's doubtful that MSE or any other anti-virus/antispyware application would install (or install properly) on an already-infected computer.
You have two choices:
1. Back up your personal data (none of which should be considered 100% trustworthy) then format your HDD and do a clean install of Windows.
NB: A Repair Install or In-Place Upgrade will not fix an infected computer!