What is this like?

I currently have (1) 512MB PC2-4200 of RAM in my computer right now. I was thinking about also getting this

http://www.directron.com/vs512mb533d2.html



What do you think? Is this good RAM? Should I beable to use dual channel?

It's standard value RAM. Nothing special about it but it should work well for you. I don't see any reason it wont work dual channel with what you have.