[TGB!]

Just download the FLASH trial, it has preset templates that will let you set up what you want - or you can just design the interface in PHOTOSHOP and import your creation into FLASH (since they are now owned by the same people - like Peanut Butter and Jelly).

All you really need are three buttons (each on controlling each movie playing). Once each video finishes youll tell flash to pop right back to the interface.

Your biggest problem is going to be ActionScripting what you want to happen, but their are tutorials out there that cover Basic ActionScripting and what you want to do - so you dont have to get into the more advanced stuff.

It however - is easier than it looks - just spend a day reading about ActionScripting and youll be fine.