I had sync'ed my iPhone with my previous OS install some time ago and it's been ok for me for a while. However, since rebuilding to Windows 7 I haven't gone back and set up sync again. Just didn't need it. Podcast's and app's I could get directly from the iPhone. I'm running out of space now though and I'd like to modify the play list a little. As I'm sure everyone knows, when you sync to a new PC it says it wants to associate to that PC and erase everything you have on the iPhone. I don't really care about the music or the podcasts because I can get all of that back pretty easily. However, I still have the Netshare app that was removed from the App Store and I didn't want to lose that.
I did some googleing and suprisingly found little help for this. All kinds of comments about sync'ing to 2 PC's but none that addressed my specific problem. Probably because it's pretty simple.
Right click on the iPhone in iTunes and "transfer purchases". It's as simple as that.