Windows Vista

I purchased a new computer because I had to send my old laptop to a repair center and I didn't want to wait for it to get back. It's a Toshiba Satellite A215 7422 with Windows Vista Home Premier Edition installed. My immediate question is this: every now and then the screen goes blank and I'm faced with a blue-black nothing. No error or blue-screen-of-death, nothing. I reboot and everything is fine. I haven't had to deal with these problems in XP for a long time (don't remember which service pack fixed any issues), so I'm not really happy about this. Anyone know what's wrong? Second, more generally is there a good site for tweaking the OS for optimal performance taking into account my needs? Since XP worked so well I haven't had to make recourse to such a site in a very long time. The main one I used ...