Formating

Do you want to format your system completely or just a partition (drive which is not used for installing operating system)? If you format a hard drive completely then you will have to re-install the operating system again and then only you will be able to install your required softwares.
 
Best method if your planning on formating due to a virus is use GW Scan from western digital and make a boot disk from it first so you can rezero the hard drive to factory settings to prevent any further issues from popping up. should be easy to find it.