Default [Q] Windows 7 won't recognise Asus TF300TG anymore

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. I have found how to unlock the tablet and i would like to root it as well, so can install later versions like kitkat on the tablet.

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

Thanks
Glenn