Download SANDRA from the download Library (link abve) - then test your system.
Sandra Standard (September, 2002)
Keep your computer running smoothly and efficiently with this set of system diagnostics and benchmarking tools. You also get performance tune-ups for all your hardware devices and subsystems. Reporting features let you easily save, print, fax, and e-mail detailed system reports. This version offers additional modules, including CPU, multimedia, network, and memory-bandwidth benchmarking.
More info would be useful
Post sandra results - it should tell you any problems and fixes.
Motherboard, processor, graphics card etc. + drivers