Question : Problem: how do I use memtest without a diskette?

I intend to do the test remotely.

Answer : Problem: how do I use memtest without a diskette?

As far as I know, unless you are running linux, you can't. It may be loaded via LILO on Linux systems.
Memtest requires a restart of the PC to boot to live media such as a floppy or a cd in windows systems as it is a standalone program.