Needs to be customisable e.g. computer usage (low, medium, high). Minimise-able. Instead of remove duplicate files, option to compress them (as a backup copy)

Seriously?!?! I fail to see how any of this is going to be an improvement to the program itself. Firstly the reduction of system priority to the program. This would only be useful if your running a program as a service or in the background rechecking on a timer. Nobody is going to keep using this daily. Your going to run it and observe the results and proubly not run it for sometime, eg a month later. Making an option to backup what are duplicates. This is really sily, its just like saying you want to make a backup of your whole system so you have a 1:1 copy of a file. If the file wasn't going to exist on your system any more, then someone would want a backup, not when the file exist on the system still, its a dupe, its NOT needed.