question on reformatting HD

i have a question on reformatting my macbook pro's hard drive. i did a search for this but really couldn't find the answer i was looking for. ok, i backed up my hard drive using time machine to an external drive. i want to reformat but i have some software that i lost the discs and the key. will i lose those programs if i reformat? or should i take the entire program off my hard drive and put it on the external so i don't have to reinstall it when formatting is completed? i have snow leopard with 180 gb hard drive and 1Tb external hard drive.

I think the program you're referring to is already in your back-up with time machine.

If you however have an iso of the cd (with key) stored some place, that might not be in the back-up, so then it would be advisable to do so.

Just reformat, restore your back-up, and you should be fine.

let me know...