Ever since we saw this post over at the Virtual PC Guy’s Weblog, we have been using Dave Whitney's Free Defragmenter on our virtual machines’ dynamic VHDs to improve the compaction process. The results so far have been great – we have managed to shrink dynamic VHD files to levels far beyond what we could with the standard Windows Disk Defragmenter.
This week I decided to do a little spring cleaning on my work laptop. I installed Windows on it around 2 years ago, and have been installing/uninstalling tons of software ever since. The machine, predictably, had become painfully slow.
Yesterday I managed to remove about 3.5GB of old software and files, leaving the hard drive horribly fragmented. So I decided to leave the Whitney’s defrag tool running overnight… today in the morning I am surprised on how responsive it is! Outlook now takes a few seconds to startup (with a multi-GB pst file), compared to over a minute yesterday. And I can’t believe how quickly the Windows Live Messenger and Visual Studio .NET 2005 started up. I was so surprised, I even decided to write about it here! 
HOT TIP: I also recommend an utility called CCleaner to help you optimize your system. It removes all sorts of temporary files and safely cleans up the Registry. I my laptop it freed up around 750MB!