Are you saying that you DO have malware? Also, do you mean a reinstall of Windows vs. restarting your computer (reboot)?
If you have the disks for your Microsoft programs (Office, I am assuming) and a Windows installation DVD, you can always re-download your Steam games. If you have malware, I would reinstall Windows just to be safe. But make sure to back up your documents to an external drive, and have the latest drivers ready to go for after the installation because your network adapter probably won't work until you install the driver manually, and do all of the Windows Updates.