Here're the Screenshots guide on how to make partition active in Windows 7, the test environment is Windows 7 32-Bit Edition, of course, it also works on the 64-bit edition, the final screenshot we attached in Window 10 64 bit Edition. Click each picture to enlarge and you can use arrow button to go through next or previous pic. (Partition Expert has both 32-bit and 64-bit edition, install it or directly from the portable package)
NOTE:
- If you some error messages show when running those command, please run "cmd.exe" as administrator
- One disk can only have one active partition
- Active partition is used for system running, there's no need to set other data partitions as active