A virus infected computer is one of the worst nightmares that you can get when troubleshooting.
Not only is it a very long process if you do not wish to reinstall your operating system, most of the time this process is a constant hit and trial that does not always lead to good results.
There are also chances that you may do more damage to your system than repair.
Only if you are sure of the steps that you need to do should you proceed.
Make sure that you keep a note of the types of errors that your system is giving you.
This will help you search online for similar errors and how to completely get rid of them.
Looking for a solution online will require you to do a diagnosis of what, when and how the issue with the virus started.
If you are able to find the cause then your problem is already half solved.
You should avoid searching or using the internet on a virus infected computer unless you have an anti virus program that is working which is unlikely as your computer would not have got infected in the first place if you were using a good one.
Use another computer to look for a solution.
Manual removal of a virus involves getting into the registry of your computer and deleting the files associated with the virus.
You should always double check your steps here as you may as well end up deleting something of use.
If you have another computer that has an anti virus program installed and also an external hard drive you can also put the infected hard drive and connect it to the computer and scan it with the anti virus program there.
You must be careful here as there are chances that the other computer may get infected if the anti virus program is not good or updated.