Need Help!

I am about to Purchase a Dell computer again! I am a videographer and edit wedding video's. I edit with Pinnicle and Adobe Premire. I will be editing with Avid Express in the near future..  This program requires XP Pro. It will not work with Vista!  Is there anyone using any of these editing progams, and can tell me what they think about dell computers with these programs.

 People are telling to go with Vista but I know that Avid will only work with XP. If this is not the right forum can you tell me which one I better direct this one too!

Thanks for your help!