My steps for copying to Win8RT
The easy way
1. Using Tivo Desktop Plus, set up my transferred shows to convert to iPad mobile device. This puts the converted .mp4 in a folder (by default, mine is in User\My Documents\My TiVo Recordings for Portables\iPad). There are a bunch of things you need to do to make sure Tivo Desktop is working properly, with the Tivo Server process running in background to convert the shows. See the Tivo site for that set up if you don't know how.
2. On my Surface, went into the 'Desktop' and mapped a shared drive to \\MYPC\Users\[my-user]\Documents\My TiVo Recordings for Portables\iPad. Click the box to remember it/reconnect next time.
3. Once you get the folder on your PC open on your Surface, you should see a folder for each show, with 1 or more episodes in the folder(s). Either click the checkbox next to the folder or go into the folder and click the box next to the episode(s) you want.
4. In the toolbar, there is an icon that says 'Copy to'. Tap/Click that, and a drop down appears. Select 'Videos' and the copy should start. Once complete, the videos will appear in your Video app in the 'My Videos' area (swipe all the way to the left).
It's worked fine for me. Make sure you have the latest Surface updates applied. When I initially got the surface, it sometimes didn't seem to support an iPad compatible MP4, but I've had no problems since a windows update was pushed (~2 weeks ago?).