m312L1n, have you tried it? It'll scan for errors & tell you how many problems it finds but will NOT let you repair anything unless you pay for it (from what I remember when I used it 2 years ago). IMHO, most of the errors it lists are 'false-positives' - to make one think something is wrong when it isn't. Plus most of these errors are probably minor & one doesn't need to pay to repair them.
To see what some users (at download.com) think of PC Bug Doctor click here. OK, may not be the best place to look for a good, unbiased opinion!
Optimizers (& Diagnostics) at download.com - sorted by user rating - PC Bug Doctor received a 21% positive rating, so will appear much lower down the list - click here?
You know if you have a problem, you can post it here & someone will tell you how to fix it, give you a link or tell you to download programs (free ones as far as possible) to fix them : ) G