If you are an advanced or power user, or use Vista on a workstation, you might have noticed a slowdown experience, starting around 2-3 months after the fresh install. There is no secret behind this phenomenon - Vista massively caches system files in order to speed up the responsiveness of the operating system.
Unfortunately, their Shadow Volume Copy does little more than increase disk fragmentation and in combination with constant indexing, slows your computer down instead of speeding it up. Annoying, isn't it?
With Service Pack 2, Microsoft cleared Shadow Volume Copy disk cache, which wasn't exactly limited under the default mode. This automatically resulted in users reporting freeing up tens of gigabytes of free space - up to 40GB was liberated. While there is several guides on the Internet which show you how to manually remove or impose a limit for the always-running always-annoying "SVChost.exe", the fact of the matter are that you would lose at least 1GB of space or 5GB [recommended by all guides as the minimum figure].
Here comes Service Pack 2 with its almighty compcln.exe and allegedly, all that it does is cleans up older files, such as remains of the original Vista installation or the SP1. At first looks, the story holds ground, but the fact of the matter is that compcln.exe clears up Shadow Volume Copy out. Yep, all hidden and non-reachable files are gone. If you haven't tampered with SVC and removal guides, you might gain even up to 40GB of free space, and that is nothing to be sneezed at. Especially if you are running the Vista OS on a SSD drive.
Good job Microsoft. It only took you guys years after the Vista came out to finally start cleaning up the garbage that wasn't supposed to be there in the first place. Seriously, we would like to meet a team of genious Microsoft-folk who thought that continious shadow copy combined with Vista indexing and the fact that hard drives get fragmented all the time - won't slow the machine down. Candidates for the [non-existant] computing category of Darwin Award, that's for sure.