Sorry Bubbles - but I'm presuming you mean your e-reader ?

[ Not being pedantic, but I'm always moaned at if I use the wrong terms  ! ]

You need to de-authorize the reader from your old PC, then go through the whole registering process again, only with the new PC .

Haven't done it myself, but there have been a few threads on this, Seach should bring them to light - although I don't know whether the T1 's been covered yet.

Check your PM's.