hey Patrik, not all times System Restore fix virus problem, especially that modern virus techniques infect system restore and they actually prevent you from going back to an earlier point.
I spent 5 years as an IT Technician and I have some good techniques that might help you hopefully.
First try system restore but if it fails then Please try to follow my steps in the proper order.
I. Please Download the Following Programs but Don't Install or Run Any, Just Download Them and Put Them inside Folders for future Use:
1. Download a Free Virus/malware Scanner Program called "ComboFix" it is around 3MB
http://download.bleepingcomputer.com/sUBs/ComboFix.exe
2. Download Antivir Antivirus, Free Antivir Version with its Latest VDF Virus Update Definition
http://www.avira.com/en/download/index.php
http://www.avira.com/en/support/vdf_update.html
3. Download free Verison of Malwarebytes and after installing it run online updates its update patch is small
http://www.malwarebytes.org/
4. Download CCleaner Program
http://www.ccleaner.com/
II. Procedures to follow after downloading the need software's:
1. Uninstall AVG Free Antivirus
2. Disable System Restore
3. Run msconfig from Run dialog box and Disable all Startup Programs
3. Restart your PC and Go Into Safe Mode
4. Run Combofix in safe Mode (it may restart but it is a normal behavior)
5. Install MalwareBytes, Do Online Updates, Return to Safe Mode and Make Quick Scan
6. Install Antivir with the Updates (Offline Update is done after installing Antivir, you opne it and in the Menu you go into Update Option and Choose Manual Update)
7. After Installing and Updating your Antivir. Go to Safe Mode and Scan your Drives
8. Install CCleaner, run and Clean your PC and also Run and Clean the Registry from CCleaner
Please Note Such Technique Works 90% of the time, but with badly infected Systems the Windows might stop entering your Desktop and will need to Boot from your Windows CD and Repair your Windows, doing a Repair Installation Procedures, things happens if your Windows\System32 Files have been infected badly and cannot be repaired by your Antivirus Antivir so it deletes them instead of Repairing Them, but the good news is that Antivir will ask you and you will decide to Delete or Not.
Good Luck, and for any info let me know.