When I try to deploy IE8 group policy to users that already have IE8 installed the group policy object uninstalls and then re-installs IE8.
Is there anyway to prevent this?
In order to prevent your IE8 policy operating on computers that already have IE8, you need some way of scoping your policy so that such a population is outside of the scope of your policy.
You can do this by
Its kinda an Achilles heel of doing GPO installs in my experience. The GPO looks to see if it installed the program yet or not, it doesn't care if the program is installed already. Its kinda a feature really since it lets you control exactly what application and version is installed.
Depending on how you handle things deploying IE8 through WSUS may work better since then Windows updates checks and compares the available downloads and only downloads what it needs.