Get an external drive, firewire or USB2. 7200RPM. Keep your materials off the primary drive. Bump your ram up, if you can afford it. Your processor’s a bit underpowered. Vegas will run in your machine because it’s designed for minimum platforms. However, when it comes to rendering out the final project you will pay the price for not having the hardware. It will take a very long time to complete.
Premiere, Vegas, Edius and even FCP are entirely at the mercy of computer’s specs.