idk if you are acknowledged of this or not but w/e you do, DO NOT trust anything that's PC Tools Registry Mechanic 2010 or 2011. doesn't matter how updated it may be, DON'T TRUST IT! that includes Spyware Doctor. it's a fake software that used to hack into your PC while it fake cleans it making you think that your computer is safe, but in reality its either letting more infections onto your PC or adding to the cause. this of course causes slow performance and serious lag and even crashes due to Malware and viruses that had harbored into your PC. Spyware Doctor and other software sponsored from PC Tools Registry Mechanic are also known to lock-up your legitimate programs that you need to get into on the regular basis such as anything that needs administrative permission to access. so w/e you do don't buy or even try it. you'll regret it.
my advise, although i know alot of us are smart enough to do this on our own, is to go to a website like this one:
http://social.answers.microsoft.com/Forums/en-US/vistasecurity/threads?page=6
and you can find answers to what type of software is best suited for your PC and if its safe to use.