Hi,
I believe so.
Go to
http://www.seelhofer.ch/mad/ to their download section and download MyCPU.
MyCPU: MyCPU is a small utility to find out which cpu is installed. It shows vendor, type, model, stepping and speed information. Additionally it scans for features like MMX, 3dnow and SIMD (ISSE). Finally, it is able to read cache information such as the size of the L1-data & -instruction cache and the unified L2 cache.
Also note that going from a 266MHz cpu to a 300MHz cpu will not give you a noticable difference!