A full wipe should never be necessary. You'll be amazed at how much improvement a good cleanup can make. If viruses are really the problem, run Rkill followed by some AV tools.

1. Run Rkill to terminate running malware
2. Run Hitman Pro [ Register or Signin to view external links. ]
3. Run Malwarebytes [ Register or Signin to view external links. ]
4. Run TDSSKiller anti-rootkit [ Register or Signin to view external links. ]
5. Install Avast and run a boot-time scan [ Register or Signin to view external links. ]
6. After the scan has finished, defragment your hard drive.
7. Uninstall programs you don't need.
8. Run Disk Cleanup.
9. Using msconfig, disable services and startup items you know you don't need. If you don't know what it is, don't disable it.
10. Reboot.

r00t wrote A full wipe should never be necessary. You'll be amazed at how much improvement a good cleanup can make. If viruses are really the problem, run Rkill followed by some AV tools.

1. Run Rkill to terminate running malware
2. Run Hitman Pro [ Register or Signin to view external links. ]
3. Run Malwarebytes [ Register or Signin to view external links. ]
4. Run TDSSKiller anti-rootkit [ Register or Signin to view external links. ]
5. Install Avast and run a boot-time scan [ Register or Signin to view external links. ]
6. After the scan has finished, defragment your hard drive.
7. Uninstall programs you don't need.
8. Run Disk Cleanup.
9. Using msconfig, disable services and startup items you know you don't need. If you don't know what it is, don't disable it.
10. Reboot.

My two sense would be to have disk cleanup before defragmenting so that the system can move files to the space that might be freed up from cleanup. Not a big deal though.

If none of the above works, I recommend doing a clean wipe of the computer with a disc you can buy online. Worked well with my 1990's desktop.