Yeah, reformatting is a little drastic!
Over the past few years I've dealt with every kind of spyware/adware/virus going, and none have needed a format and reload.
If you think you may have adware/spyware Bazooka is a good free tool, and AVG isn't bad as an Anit-virus.
I use Macafee firewall, and it's spot on, but you do need to pay for it. There are a few good free firewalls floating about.
Please try not to use the Microsoft firewall, it's not that good and keeps getting hacked/bypassed.
If you need any advice pm me, I can always connect remotrly if need be to sort you out!