What are the symptoms of the virus? If you can get into windows try running the free program malwarebytes. If you are unable to get into windows, or if windows is rendered unusable because of a fake antivirus program or something, then describe exactly what is happening.
Your system should have come with a factory restore dvd, or a recovery partition on the hard drive. Consult the manual that came with the system for directions on how to access and use the recovery tools.
Be sure to back up your data to another system before restoring, and once you have retrieved what you need, scan the recovered data on the other system for viruses before doing anything else, so you do not infect the system you back up to, or re-infect the Acer.