This v9.0 is the latest version of Registry Mechanic [i.e. in effect Registry Mechanic 2010], and it is compatible with Microsoft Windows 7 (32bit, 64bit), Windows Vista SP1+ (32bit, 64bit), Windows XP SP2+ (32bit) on the PC. This latest version doesn't really offer any extra features over the previous RM 2009, it is in effect a further one years licence to use the latest program. If you already have Registry Mechanic 2009 there is an annual licence renewal route via PC Tools website, but often boxed versions such as these are cheaper via Amazon.
So what does Registry Mechanic v9.0 do? Well, if you are the type who constantly loads and unloads software and games chances are your PC system registry has got a lot of rubbish lying about in it. Manual editing of the registry can be done with Windows RegEdit which is fine for simple edits of a known problem but one false step and your hard drive could become unbootable requiring a complete reformat and install of Windows [and any data on the system drive lost]. The thought of that naturally puts off most people from playing around with the PC's system registry. However if your PC is having a lot of problems loading [very very slow to boot up and a lot of disk chuntering] chances are something unfortunate has happened to the registry and Windows is rummaging about looking for lost links etc... Or do you get frequent unrelated system crashes and a lot of odd cryptic Windows error messages, or is the PC now simply moving at a snails pace?
A slow system speed might be just because your hard drive needs defragmenting or an error check, so do that first [Goto: Start, Control Panel (category view), Administrative Tools, Computer Management, Disk management]. Also try deleting 'temporary files' under internet explorer's Tools, Internet Options. Alternatively your system hard drive may simply be full up, as you ideally need at least 25% free space on it, 15% minimum [if so, uninstall games, delete rubbish, and/or get a secondary hard drive]. Also be aware of any hardware problems like the PC's S.M.A.R.T. system reporting hard drive errors [switch it on in the PC system BIOS] or the hard drive making unusually loud clicks - both signs of imminent hard drive failure and data corruption. However if all that doesn't cure the problem it's quite likely that this bit of software, Registry Mechanic 2009, will help. Load the software, register it online [wait for the updates], and run the registry check. It will come up with a load of registry errors, say fix them, wait for the OK, and then restart the PC. Hopefully the computer should now start-up much faster and be more stable. Registry Mechanic even sets a system restore point so that you can undo any changes it has made, in the unlikely event something useful or crucial is accidently removed. The software can then optimise the PC registry to further improve PC speed. All I can say is that if your system is experiencing registry problems, this program really works and it is highly recommended by techie magazines like PCPro. However, if your PC is working perfectly, certainly don't bother installing or running the software, as it might do more harm than good and can't really offer much benefit anyway. I have used Registry Mechanic for many years and it does work well. Once the PC stability problems are resolved I wouldn't run it very frequently, if at all, or leave it running in the background, as it might chip away at the registry integrity. More likely it will affect non OS software though [e.g. Adobe], and besides using the Registry Mechanic 'Undo' option, you can simply re-install the problem software [as it may have a registry error anyway].
I've never known Registry mechanic affect a crucial Windows file [but make sure RM is updated to it's latest version]. With Partition Magic I have lost whole disk partitions of data when it's operation failed, but problems on this magnitude have never happened to me with Registry Mechanic. However, if your system seems to be in need of software like Registry Mechanic 2010, head straight for a comprehensive backup of all important files, documents and photos first. In fact this year I have just lost an entire XP installation to registry corruption, that prevented Windows booting up at all on my main home-office PC, even in safe mode - a very complex temp fix from Microsoft allowed me to recover and backup files, but I lost all my emails for 2008 - and no, Registry Mechanic wasn't installed on that PC.
That said if any computer of mine is experiencing very serious problems after a dodgy install or two, I always reformat the system C: drive and re-install Windows - and believe me that is like a breath of fresh air to any PC. This assumes that you have wisely formatted your hard drive into two partitions so that all your data is 'safely' [well relatively] on the non system D: data drive [use software Partition Magic for this if your drives already have Windows/data on them - and back-up that data to DVD ASAP]. I stopped using Registry Mechanic a year or so ago, as this software only runs for a year after install - after that you need to buy the licence again [renew it] to get the crucial software updates and email support. This Registry mechanic v9 is for XP, 2000, Vista and Windows 7 only. However you can still buy the old RM Version 7 from PCTools if you have Windows 98/ME. Previously if you suspected PC registry corruption but don't wish to shell out on Registry Mechanic, you could use Microsoft's freebie offering 'RegClean', which was less sophisticated & quite conservative in it's repairs. However Microsoft's trustworthy RegClean's no longer available for XP/Vista, so for a registry repair freebie you'll now have to trust the likes of the [well respected] CClean that includes a 'registry cleaner' utility. The Australian firm 'PCTools' that produces Registry Mechanic v9 makes other security software such as the respected anti-Spyware program 'Spyware Doctor', that goes beyond that offered by standard PC anti-virus software.
How does Registry Mechanic v9 work? Well: "Registry Mechanic uses a high-performance detection algorithm to quickly identify missing and invalid references in your Windows registry. These problems can occur for many reasons including being left-behind after the un-installation or incorrect removal of software, by missing or corrupt hardware drivers, or orphaned start-up programs." Now that I have teenagers in the house with their own PCs, who download and install goodness knows what, I have renewed my PcTool's Registry Mechanic v9 and sibling application Spyware Doctor licences to usefully help clear up after them when necessary.