I was asked to remove and re-install SQL Server on a host, this is usually no big deal and something that I can get done in a matter of hours. I can usually install and configure SQL Server to my standards fairly quickly. This was a bit different though. When I logged on to the server I noticed that some SQL Server components had been installed but none were functioning. I proceded to the Control Panel to remove the applications but when I attempted to do so it just hung. I let it run, as I was busy with some other things. The uninstall finally finished, hours later, and I also noticed that the directory structure on the Server was nothing like it should have been. I thought that since I had removed everything I could go ahead and clean up the directories before I re-installed. Well I started to delete some no longer needed files and I could not. Kept telling me that the file was open by some other application. I fought and fought with it and finally I decided to disable the on access scanner that our AV has. As soon as I did so I was able to remove the files. I sent a note to our Virus Guy and did not think much else about it. I cleaned up everythin that I needed to and then I installed SQL Server. Again it took FOREVER to install. I let it run overnight. When I returned the next day it had an error about not being able to start the SQL Server Service. I attempted to start it manually and it failed and no useful errors were being logged. I noticed the that on access scanner was on again so I turned it off and now the service started just fine. Again I sent a note to the virus guy and finished the install.
Just thought I would share the story as others may have strange issues like I had and hopefully you will now think to look at your AV and make sure that it is configured properly.