Today I attached a 250 GB USB drive to my ThinkPad to clean it up a little bit. I never thought that there might be a problem, but I was certainly wrong :-) There was an old Windows XP installation on the drive with a couple of apps and some of my docs. I thought that I could delete all apps etc, keep my files on the drive and use it as my "new old" external storage. I deleted almost every folder, including the "Windows" directory but on the "Program Files" folder a window came up that told me Vista is not able to do what I want it to do... "Try again" or "cancel"? I hit "Try again". The very same window came up again... I thought it might be a problem of the ownership, so I replaced that by MY user for all the files and (sub)folders. Still unable to delete it :-( I started to delete the subfolders manually to see which one is causing this headache. It was this funny Z:\Program Files\Common Files\Adobe\Acrobat\ActiveX\ folder!!! The files in there seem to be undeletable and apart from the fact that I really don't know why Adobe is doing this, it seems that a couple of more people are unable to delete them (see here (livejournal.com) or here (adobeforums.com).) I found even more on Google and people suggest to install various apps, boot a Linux LiveCD, ... Well... A BackTrack CD was lying next to me, but I was too lazy to reboot my ThinkPad :-) After about 3 mins I found out that only one check box is necessary to delete this stuff. Just do the following steps:    - Right click on the "ActiveX" folder    - Select "Properties"    - Go to the "Security" tab    - Click on the "Advanced" button    - In the "Permissons" tab hit the button "Edit"    - Check the box called "Replace all existing inheritable permissions on all      descendants with inheritable permissions from this object"    - Hit "Ok" on all of the three open windows.    - Delete the folder! :-) The folder and especially the files    AcroIEHelper.dll    AcroPDF.dll    pdfshell.dll are now gone! Depending on your user and/or configuration, you might need to take ownership of the folder before doing that, but at least you don't need to reboot your machine, install some strange tools, pray, ... Good Luck :-) Disclaimer: Use on your own risk!! Don't delete the files if you still need Acrobat!!! Don't use this HowTo if you don't know what you are doing!