registry

I downloaded a program to open up a file that had an extension I was not familiar with. No problem- I thought. Three days later I happened to go into explorer and the program had “taken over” a number of files. Deleting the program did not restore the original associations. Luckily I went into DOS, SCANREG /RESTORE and the last 4-5 dates of the registry were there and I simply restored the 5th day back. I got to thinking if I had waited much longer I would have been sad out of luck. Is there away of saving a registry that can be used whenever in the future?