Default [Q] I cant connect asus tablet to windows 7 computer

I have a asus transformer tf300tg and when i connect it to the computer it is not recognised. This happened i believe after i restored factory settings, and then upgraded immediately from ice cream sandwich to jellybean without enabling developer setting in ics. I have jb 4.2.1, and build 10.6.2.11. I have changed jb to developer and enabled usb debugging but computer wont recognise the tablet. My tablet is locked as well, and would like to root it, so can install later versions like kitkat on the tablet.

I think i will need to restore factory settings again, then change to developer then add jb again, or is there a better and quicker way?