THE most suitable time to 'convert' Windows users into GNU/Linux users is when Windows betrays them, usually with viruses or malware. The Register says that Microsoft advises users to reinstall Windows in such a circumstance:
Microsoft is advising users to reinstall Windows if they happen to be unfortunate enough to get hit by a particularly vicious rootkit.
The Popureb Trojan sticks its tendrils so deep into the operating system that the best option is to nuke from orbit return machines to their original configuration. Any files that aren't backed up will be lost in the process.
If you have to reinstall the OS of your PC to keep it running, consider installing GNU/Linux to stop the foolishness.