Need help in transferring apps from itouch to PC..?

I bought my itouch to another person and it already have a lot of applications on it. I really want to add new applications using my computer but i'm afraid that if I am to sync it, all the existing applications would be erased because at the first place, I didn't have the applications on my itunes. It's just on my itouch, now my problem is, how can I transfer it? I clearly said that i'm transferring applications right? Those software does not transfer applications, it only transfers music and videos.