I'm told this is a somewhat common problem, but is there anyway to isolate what causes it? We only host a few web applications on this server. But every so often w3wp.exe will suck up all the RAM on ...

I've got a windows 2003 server running a number of websites in ASP. I've noticed that as soon as the web service is turned on the w3wp process jumps up to 99% CPU and eats up memory on a steady basis.