I did this years ago (no longer use Metastock though)....
Install Metastock to a second PC
Extract all areas of the registry related to the indicators
Copy all files in Metastock folder (I think the main one you needis MSFMLxx.DTA where xx is your version number or something like that).
In the future:
Buy yourself a couple of external hard drives and do regular system image backups to avoid this whole issue.
Also copy-and-paste your formula to standard text files to make it easier to recover too