If you have XP installed you can go back to last known good configuration by pressing F8 before windows starts up and select last known good configuration, if that does not work you'll have to start up in safe made and get rid of what ever causes the problem, to get rid of the adware you have to remove the source file of it first and then go in the registry (regedit in run box) and remove all entries concerning the adware or spyware, to make it easy you can use Bazooka adware remover it shows you what you have to remove it is free and finds all spy/adware on your PC but make sure you have udated the Bazooka ad/spyware scan list first. If that does not help you can try to let windows repair itself with the cd but most of the time that is a waste of time and a re-install might be the best thing for your pc.
PS
If you remove entries in the registry make sure you remove the correct ones, removing the wrong ones can cause complete system failure and a re-install has to be done then.
I hope this will help you out.