Since it was not booting from CD, I brows the CD and ran the setup file. Initially it was not allowing and asking for administrative password. But after disabling the antivirus, it became possible to run the setup file. I opted for Advance option(fresh installation ie. not upgrade), where partitioning option is available. After all the files got copied, it displayed the message that it wants to restart. While attempting to restart, it only displayed a blue screen. After that neither it loaded window from HDD nor from CD. This was the situation when, initially I had sought the help from Tom's guide. That time I was unaware about any virus infection. It is only after getting it formatted by the service center and OS reinstalled, when I installed the antivirus, that I could know about virus. I had brought the CPU from the service center on last Saturday. Sunday I found the problem. Monday, again I took it to the service center and got it formatted and OS reinstalled. After that when I still found the virus that I contacted you as per advice of Mr. Derek from Tom's guide.
Now window does not get loaded and does not boot from CD also. So, is there any way that I can format it and install OS?