Unless you have a powerful computer (paticularly so in respect of RAM)then you will always struggle with any video/imaging software. I personally recommend at least 1Gb of RAM.
However, three hours does seem a little excessive - have you tried minimising all non-essential background processes?
I was intrigued when you mentioned Ulead. I also trialled Ulead (video) some time ago and basicly threw it out after a few days because it did seem "power hungry." Similarly, I still have a copy of Uleads Photoimpact and same comment really - very power hungry and in my personal opinion, is inherently unstable. Perhaps a manufacturer issue?
May I personnaly recommend the Pinnacle video suites to you.