I would never pay money for a "computer specialist" to run a virus scanner on my computer to see what's the problem - even if they're able to "fix it" without doing a reformat (which is a 150% guarantee all viruses are gone), it's still a possibility the virus software they've installed on your machine didn't pick up certain entities such as ones that linger in the registry and like to change around defaults where as a virus software won't change them back.

I'd go with the reformat process, it's a safe guarantee if you know how to do it - don't waste your money on a process that takes exactly 30 minutes once the installation starts installing.