Multiple viruses-svchost.exe, infostealer, hacktool rootkit

I have Symantec antivirus corporate edition (provided by my school) and am having some virus problems. It started a couple months ago. I believe the virus was names hacktool rootkit or something of the nature. There were hundreds of them and Symantec kept on catching them, but it seemed like they were being created faster than they could be caught. Then the infostealer virus started. For a while I had both bothering me and Symantec couldn’t stop it. After lots and lots of scans, those 2 problems have been cleaned (or Symantec isn’t finding them anymore). Now I have a svchost.exe virus. Symantec doesn’t notice it.  I found out by opening my task manager to find hundreds of processes running. When I start my computer I have around 50 processes running. If I leave my computer on, hundreds of svchost.exe processes form (the number slowly increases). I have tried solutions found on various forums, but they have not worked. If you think you can help, please do so.