There are many schools of thought on what to do if you computer gets a virus, here are the steps that I suggest you follow.
1) Stop all network access. This means, disconnect form any network connection, including the internet. This means disconnect any network cables, wireless, or other network connections. This ensures that if there are any viruses that are dependent on network connections, their capabilities are restricted. Furthermore you then prevent propagation to other networked computers.
2) Document what you saw that made you suspect that you have a virus. This includes the way the computer operated, any screen warnings, pop ups, or any antivirius warnings. The better the detail, the more effective the response to the virus based on researching the root cause
3) Shut your computer down. Depending on the type of virus, the longer you leave your computer on, the more severe the damage. Shut down as soon as possible.
4) Verify your back up, have your system restore disks, and software installation disks. Again depending on the type and severity of the virus, the system might not be able to be recovered without formatting and reinstalling the operating system. If you do not have back ups, system restore disks, or software installation disks, a different strategy, more costly, might have to be used in order to recover your system and its files.
5) Attempt a virus removal on your own, or contact Collaboration Lab for virus removal. We offer a free 15 min. estimate, so if you are hesitant about cost we can give you not to exceed estimate before starting.
One other point, it is a good idea to change your passwords that were used on that computer. Again, dependent on the type of virus on the computer there is a possibility that you passwords have been compromised. Better safe than sorry.
If you have any questions, feel free to comment or contact me.