For WCG(UD) agent install to other partition or just plain outside the C:\Program Files\ structure.... e.g. make it C:\WCGUD or for BOINC C:\BOINC and you should never get questions like permission or a Redmond force to push u into reinstalling.

I use BOINC on Windows Vista with no problems. I created a user for boinc purposes and installed BOINC as a service using that account. The account is granted 'Log on as a Service' rights through the install. I then went into the Program Files directory and assigned the BOINC user account full rights to that directory and all sub directories and files. It runs all the time and I've not no issues with running other applications, including CPU intensive applications.