How to measure disk performance? [duplicate]

A friend has asked me to perform maintenance oh his computer. The described symptoms point to a performance issue with the hard drive. I want to objectively confirm this suspicion by measuring the performance of his 5400 RPM disk.

Which tools would you recommend for this job? Are there any (published) standard guideline numbers that I could use for the purpose of comparing my findings?

I always use HDTune. Simple, 'fast' and you can compare test results on their website.

IOMeter is great for measuring disk performance, there are several sites available that carry reference tables (I used one for VMWare based PC's, so I suggest you google for alternatives :-) )

EDIT: Found a very nice table on Tom's Hardware, I'm guessing the "workstation" profile seems to fit quite well...