Welcome to Bleeping Computer. You ask a good question.
Registry Mechanic and High Jack This are two seperate tools, designed for different purposes. Using Registry Mechanic may be helpful, and maybe not. Anytime you mess with the Registry you run the chance of your computer not running correctly, or even booting. Automated programs used to 'fix' the registry can also be too agressive and hurt your operating system.
Personally, I would recommend against using any registry 'fixing' program, unless you are very knowledgable in the ways of Windows Registry.
HJT is a tool used to diagnose malicious software infections. Although it has the capablity of altering your registry when told to, this should NEVER be done unless under the direction of a malware expert. BTW, running HJT and remove some registry entries does not remove malware, contrary to what some websites and unskilled users might have you believe.
Edited by Albert Frankenstein, 15 March 2006 - 08:19 AM.