I'm in the same boat, sort of. I just reinstalled my W7 operating system, so what I did is copy all of my music, videos, apps, EVERYTHING onto an external hard drive. I even copied over my backup files (see: very very important
)
I'm just going to transfer everything back over to my internal HD today, after installing a fresh iTunes 10 onto it. I'll then connect the iPad and iPhone to it, and hope that everything is good to go. The only thing I'm a little hesitant about is making sure my schedule and contacts sync over to MS Outlook (from the iDevices) well enough that only a few minor changes will be needed.
Unfortunately, if you didn't copy over all your music, videos, all other files, you may be up a creek. Unless you downloaded everything from iTunes, which in it's own way will take hours to redownload everything..