Generally speaking, registry "cleaning" programs are a scam. I refuse to believe they do anything useful until they provide some kind of meaningful description of exactly what they do. Things like the basic selection criteria used to decide which registry entries can be removed. Until I see something like that, as far as I'm concerned, they don't actually do anything but generate a nice pretty report after a couple of minutes doing nothing.
Mostly because the registry has so little to do with system performance, it's laughable to think that clearing out a few excess entries is going to have any significant impact. At best, there's an instruction in there to try and load some DLL that doesn't exist anymore, and the operating system spends a few seconds searching for it before spitting up an error message or just silently erroring out and moving on.
Registry scanners/cleaners/fixers are all scam programs designed to prey on the technically ignorant. You go in expecting this program to do all these wonderful things for you, so whether or not it actually does, your mind creates this illusion. While psychologists may disagree on the finer points of exactly how and why this happens, there's no real debate that it DOES happen.
As for your other problem... Odds are it's just system restore allocating more space for itself to store the data necessary to roll back changes should you so desire to. It will cap itself at 15% of the total capacity of your drive, which does not appear to be user configurable like in XP. However, it is a small price to pay when you think about all the possible jams system restore can get you out of.
Hi all,
I bought new laptop - HP PavilionDV7. It is nice and very fast.
After I removed some games I noticed that my pc started working very slowly.
I tried to fix my computer with my old registry cleaner that I used on XP, but when I finished I had to reinstall everything!!
Few weeks later all these repeated again. I found new registry cleaner (Digeus Registry Cleaner) from http://www.digeus.com
I like it, it does magic on Vista! My laptop works as new.
But there is another problem - I've noticed that the total size of files on hard drive before installing games and after uninstalling them is different. It became approximately 2GB more.
How can I delete all these files that I don't need any more?
Thanks.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic