try looking at http://sqlblogcasts.com/blogs/grumpyolddba/archive/2008/01/24/perfmon-counters-thresholds.aspx
I'd also recommend the book SQL Server 2000 performance tuning reference manual
[font="Comic Sans MS"]The GrumpyOldDBA[/font]
www.grumpyolddba.co.uk
http://sqlblogcasts.com/blogs/grumpyolddba/