My earlier response seems to have 'got lost in the post'!
ALL registry cleaners run the risk of removing links in the registry that are required. VERY few actually do anything except test for dead-end links, and almost none test to see whether a link is actually going to the right place (simply because that's an almost impossible task - there may be many valid places for a registry link to go, but only one will be right at any given time, and that may change depending on settings in and outside the registry).
There is no size problem with the WinXP+ registry - unlike the Win9x registry which did have some severe size limitations. The size of the registry is almost irrelevant to the speed of a properly running machine - although it may make thre or four whole seconds difference to the boot-time!
Registry 'fragmentation is pretty much an urban myth - the registry is a compressed file held in memory, and may display lots of space in a regedit window or other display, but there ain't none in RAM!
A perfect - or even very good - 'Cleaner' would need to have detailed knowledge of every bit of software that is (or even might be) installed on a given machine. Such knowledge would have to be updated daily - and would probably be a database bigger than the OS itself!
In short - they ALL tend to create more problems than they solve in the long term. MS12-004: Description of the security update for DirectShow: January 10, 2012 Please run the CheckSUR tool from http://support.microsoft.com/kb/947821 (you'll need to look in the details for Method 2) Then zip the CheckSUR.log and CheckSUR.persist.log files and attach it to your reply. The tool can take anywhere from 5 mins to a couple of hours to run (or 'Install') depending on how much it has to do, and may exit silently - it may appear to freeze for most of that time, but be patient.