It is actually best to defragment your HDD while in "safe mode." Since your AVG or other programs want be running, you want have need or concern about them interfering in the defragging.
EDIT: added comments
You can decrease time to defragment by removing temporary files, logs, etc.
I use Ccleaner for that as it is much faster and more thorough than the cleanup utility that comes with Windows.
I also delete the "restore points" except for the last one. Unless you have adjusted the space allowed for Windows to use for restore points, there could be a few gigs of restore points.
I also don't compress files. (slow process and unless you are in dire need for space, better not to compress.
If you decide to use Ccleaner it offers the Yahoo toolbar during install. UNcheck if NOT wanted.http://www.ccleaner.com/
Edited by buddy215, 29 September 2008 - 06:12 PM.