Warning! Some of these tips are recommended for experienced users and an incorrect execution may result in halting of your operating system. I will outline three options which can also be combined.
SAVG released a free version of its Live CD with an antivirus. Using this CD, you can verify and repair a computer even if it is not
possible to start the operating system. This system can be copied on a USB disk, which can also be used as a boot disk.
The ISO file Rescue CD can be currently downloaded from http://www.avg.com/cz-cs/avg-rescue-cd-download
Burn this file on a CD and restart (boot) the system using this CD.
Detailed information can be found at http://www.avg.com/cz-cs/226386#acquire
This concerns an option to switch off undesired applications using the MSCONFIG system application. You can start this application as follows: Start -> Run -> msconfig -> enter -> Start-up.. In the “Start-up” tab you will see all applications which are launched automatically as the Windows start some of which might actually be viruses. The process of switching off individual applications can also be used to speed up the computer.
Finally, I wish to mention the HiJackThis application, which can search the registries of the operating system, and will display the recorded information. It will then allow to directly delete any unnecessary records. It is recommended to take this action in a recovery mode. The most recent version of the program can be downloaded at http://www.hijackthis.de/downloads/HJTInstall.exe