click here download and install "AIDA32 - Personal System Information".
Then open her up and follow this path...
(On the left) Click STORAGE > Then Click EIDE > Then click on your new drive at the top.
Look down the list under FIELD.
Look for BUFFER and it should tell you your cache size there.
Example: 8MB (as mine does)
Obviously you have yo have your new drive installed for Aida32 to recogonise the drive.
Also look on the drives shiny surface for a model name/number then go the manfactures website and try and find it. You'll be able to see if you have your drive and the 8MB cache.