can I move a boot camp partition to another boot camp partition?

The Mac mini (Mid 2010) - Technical Specifications has a nVIdia 320m GPU, while the 2008 most likely has an Intel GMA. For the 2008, can you look at About This Mac -> System Report -> Graphics and post which GPU it has? Also, post the Mac model identifier.

This may need more work, primarily due to GPU differences. You will most likely need to run a SysPrep to generalize Windows. Be aware that retail licensing SysPrep only a limited number of times (3).

The simpler approach is to use a tool like Winclone. The harder approach is to make a backup on MM1, install a slightly larger Windows on MM2, and then restore the backup from MM1 to MM2. The assumption is that MM1 and MM2 are same year/model with the same GPU on both.

See https://support.twocanoes.com/hc/en-us/articles/203444057-Boot-Camp-Migration-Ov erview .

If the only difference is CPU speeds, you should be fine. Verify Power Options and CPU settings. What is the version of Windows and the year/model(s) of the MM (do not post the serial number)?