When moving an existing Vista SP1 Virtual PC I wasn't able to use my mouse despite the fact that I uninstalled the Virtual PC Additions and installed the Hyper-V Integration Services.

The message you get is

"Mouse not captured in Remote Desktop session..."

In common situations you just solve this by installing the Integration Services.

Well not this time ...

After some fiddling with the virtual machine (without mouse!) it appeared that it can be solved by detecting the HAL:

Execute MSConfig, and then go to tab Boot -> Advanced Options, check option "Detect HAL". Restart is required to take effect.

Thanks goes to Folgaizer for providing this valuable information and making my mouse to work again.