This question has been asked a million times on here, so you might want to do a search for other related info, as the salespeople sometimes don't tell you what you need to know about HE machines, so here it is:
1. Keep door open after each washing load, so that it can air dry.
2. Clean the bellows (seal) inside after each load, as mold will accummulate on it, as well as on the inside of the door.
3. Must use HE detergent, as it is a less sudsing formula. It is made differently than old detergent, which is why you really only need a tiny amount of soap. Regular soap can clog up tubes and HE machines are fickle, so don't take that chance.
4. At least 1x a month or every couple of months, run the washing machine clean cycle. You can buy the tablets (Affresh, or other like brands), that will clean the inside of the machine.
Hope this helps, Tiger