But I see so little detail in your post that I can't hazard a guess yet. You might try SAFE MODE.
Vista Home Premium w/SP1
When I try to delete a contact in Windows Mail I get this error: "Windows Explorer Has Stopped Working", then it
tells me that it's searching for a solution and restarts. I've run a
complete virus scan (Kaspersky) and nothing was detected. I don't know when
this problem began so using System Restore won't do me much good. I searched
on the web and it seems that a lot of people have had this problem but I
wasn't able to find a solution.