You might want check whether mame's being forced into, I believe it's GDI mode?
I had an old laptop that I thought I could run mame in, I was AMAZED at the speed difference
The setting for my mame anyway is
#
# WINDOWS VIDEO OPTIONS
#
video d3d
the d3d is Direct3d, it can also be set to GDI, which is generally much slower, but Mame will switch to it if it can't run d3d.
Might be something to check anyway.