hi, i think a really good recovery program is needed for recovering data in corrupt sectors/clusters, spinrite recovers the data and marks sectors so no data will be wrtten to them ,it depending on hdd size it can take days to run it fully ,it boots to the cd [worth it cost ] ,so windows isn't running .http://www.grc.com/spinrite.htm
I agree that a good software is required even if it is not "bad sectors" but "many other problems" good software is necessary.
"Due to bad sectors or many other problems i have lost my important data,"
I have successful used and have read that "Recuva" is a good, free software. I am sure that the one you have suggested is much better and therefore, worth the cost. As the OP stated it is "important data".