Re: Missing a hal.dll
If you found the correct version then yes, you *could* replace just that file and theoretically it should solve that particular issue.
However, ignoring the versioning problems which would make getting exactly the right file rather difficult, you need to bear in mind the cause of this issue. If windows is complaining random dll files are missing that's usually an indicator of a rather corrupt installation! If you replace that one it may start complaining about others that are missing or any number of other problems.
So in short - theoretically, if you're careful, yes. You really shouldn't though. A far more practical (and better) solution would just be to get all the files you need off of that partition, then wipe it and reinstall.