Generally when  a program is gone it is gone in the case of a hdd crash. (well there are ways but that is a whole other story)

 

You should be able to save the downloaded program to another computer a backup key or hard drive for safe measure. I am not sure how you license the product when you buy it online. I am going to guess you have a email with a key or something. I would recommend backing up your purchase proof as well.. (print it out, copy the info to a TXT file and save it in the folder where you have the program on another system or drive, CD... Getting the program back is rather easy.... you can download it again.. Proving you own a copy... that is usually the part that doesn't go well.

 

the program is not the hard part the proof of purchase to license it again is the key when the hdd crashes.

 

M.