Trojans and spyware the virus can stay in your system, not giving any signs for a long time. If you think that the system works not stable and your antivirus did not react, then update your antivirus software through the Internet.
If you notice that began to disappear the files, or you have no access to them, it is a sign of hidden malicious software. Put this file into quarantine in your antivirus. This object will be checked for technical support and if there is no danger, it will be removed from quarantine.
Run your antivirus. Turn on full system scan for viruses and Trojans. Select the degree of verification "deep". Select the object check virtual disk partition where your operating system. This test can take a few hours. Do not click "Cancel".
To cope with the hidden viruses that does not detect your antivirus software, you need to perform a system restore. Go to "start" - "All programs" - "Accessories" - "system tools" and click "system Restore". Check the box next to "Restore to an earlier state". Pick a point "rollback" and click "OK". After the system restore hidden virus will be removed.
To deal with hidden viruses, download free anti-virus utility of disposable (http://download.geo.drweb.com/pub/drweb/livecd/drweb-livecd-600.iso) . Write on a blank disc and insert it into the drive of your personal computer. This program will scan your computer, remove hidden viruses and Trojans.