My laptop's manual says this:
"Your computer includes a 2.5-inch IDE hard disk drive (9.5mm in height) with 10GB or more storage capability. The BIOS automatically detects IDE drive types."

Is that a standard size, or is it special?

It sounds standard in size. Those small hard drives might have weird connectors though.

hmm..

What I'm wondering is if I have to go back to the place where I bought this from (which tends to have expensive stuff) or to a regular computer store. Maybe I'll go to where I bought this and lie :)

I thought size didn't matter.

Read thing's post about his monitor.. he proved otherwise.