Vista USB driver signing

First of all.. Sorry for my English.

We wrote an USB driver for an embedded application on Windows 2000.
It works fine, but now this OS in no more available.
I read this:

http://www.microsoft.com/whdc/winlogo/drvsign/drvsign_perOS.mspx

It seems that on Vista-64 bits systems is not possible to load drivers
that are not signed.
We sell no more than 100 systems a year. I guess if this certification
is too expensive for us.

Is it correct?
Any link or suggestion?

Thanks in advance,
Giacomo