Go to canopus.com's web site and look up advc-100. This box is about 250 dollars US and is perfect for what you want. Many people that use Vegas use this box including me. (of course you need a firewire card as well)
Just a warning though, you may still not get 'realtime' preview.
The faster the CPU the better it will be. When you hit any transitions / effects is when you will really start to see dropped frames.
ok thanks for yours sugestions.
Sorry my english... ;)))))
I know its not real time but with a monitor its better to check de video quality , because its diferent to de lcd from my laptop compaq. I have a presario 1500 with a 2.4G and 256 RAM...
Many thanks again, beerandchips and farss