Something is probably wrong
If the seller has all positive feedbacks and has 100+, he/she probably is experiencing a family crisis. If something was wrong with his/her computer, he/she could go use another one.
Just try contacting the seller and see what's going on. Obviously the seller does not deserve a positive (+) for this transaction because 3 weeks is way too long w/o any form of contact.
MAYBE A NEUTRAL? Actually nevermind he took your money. I say NEGATIVE if this goes on for 2 more weeks.
GOOD LUCK