Help! CPU and Memory issues

Hi All-

We have deployed a fairly standard (our first) umbraco (4.7.1) onto a cloud server with other sites (non umbraco) and are experiencing some major issues. When the site is on (app pool and iis) it is causing the entire server to slow to a grinding halt!!

The Memory (Private working set) usage is around 300KB - CPU seems to be okay.

Has anyone got any ideas what this could be?

Thanks

Kenny