It's hard to troubleshoot someone else's computer from the other side of the internet. The best I can advise is to try the following...
1 - Go to malwarebytes.org and download their Anti-Malware program. Be careful and make sure you're actually at malwarebytes.org before you go clicking on anything though. Run the full scan and fix any malware it detects.
2 - Go to sophos.com and download their Anti-Rootkit program. Run it and fix what it recommends.
3 - Go to glaryutilities.com and download their free utilities. Run the 1 Click Maintenance and fix what it finds.
The programs above excel in what they do and are aimed at the novice computer user.
Of course, making sure your anti-virus is up to date and that your Windows updates are current goes without saying.