As shown in the image, this is a directory listing of the root of my C drive on Vista (RTM version downloaded from msdn). Their is this directory with the name beginning with f4f5...
The directory contains a log file from an msxml update done via windowsupdate. I took the screenshot using Microsofts new "snipping tool".
And if I had known the following I would've not blown away my XP install and wasted a day or so reinstalling everything!
Upgrades are super-charged Clean Installs
Upgrade to Windows Vista are no longer a 'merge' with the old OS. First, Windows Vista's setup gathers old OS settings and user settings and data and stores them. Then it wipes away the old OS and applies the new operating system image (which is really fast thanks to Image Based Setup). Next, setup applies stored settings and data to this clean install based on per-component logic in manifests and plug-ins, which magically brings back your applications and data in a brand new OS. Your registry and file system are free of goo that is no longer needed by Windows Vista.