The three counters that I provided are the basics for the three main components on the computer: processor, memory, and disk. Disk Queue Length is a measure of the number of IO requests that are required but not yet handled by the IO subsystem. I've seen remarks that anything above 2 signifies a bottleneck in the disk IO subsystem.

If the Interrupts/Sec is really high, there may be a component of the system that is defective and causing a lot of interrupts which distracts the processor(s) from SQL Server.

Unfortunately, in a situation like this, you have to start very wide and narrow the search once you start getting some information.

-Mike