If I take a backup of Windows file in C:\, Will I be able to restore the file in my computer, in case my .....?

1)yes

2)no

It can be painfully done, but my experience has been that I have had issues after trying to do a full restore (even though others make it sound simple), and spent much much time fixing things that did not work properly (and in some cases money), and I am in the tech business. Here is what I do now. Backup all my software programs (including Windows Installation CD) running on the computer with License Keys/Registration info and non-security related files and documents (docs, music, pictures, etc.) to an Online Backup Service(s). I also backup (Windows Backup) the same data to a 1 Terabyte external drive, and security info (password stuff, financial stuff) to a Flash drive and keep in a secure place. Simply reinstall operating system (nice and clean) and reinstall software (nice and clean), and copy back all my data/files, preferably from external drive (much faster), but I sleep very well knowing I have Online Backup (offsite) of the same data. Less than a couple hundred dollars for the whole adventure and not necessarily the fastest method upfront, but has saved me time and money in the long run I believe. However, you will end up with a very clean/efficient machine/operating system when it is done (like new computer). Worked for me a couple times now and well worth the investment. Time consuming, but painless, and you don't really need to even be a techy with this restore method.

Just make sure that u have windows OS installation disk. Also take a backup of the setup files of all the softwares that u have installed in a disk as per the memory requirements. Some basic setup files are MS-office, driver softwares,etc.Taking the backup of the windows file won't be a solution to your virus problem.

Also using a good antivirus can also be helpful. AVG free, Kaspersky, avast, are some of the good antivirus softwares.

You can make an image of your Windows partition (or drive) using programs like Macrium Reflect. Check it out.

by making an image of your Windows partition (or drive) using programs