This driver is for Windows 98/98SE machines using the PNY Technologies Memory Stick USB 2.0 Single Slot Reader. I pulled the files straight from the CD that it came with and compressed the files in a zip archive.
The device is a rectangle shape with a light in the center. It says "Memory Stick" on the front of it.
You should also be able to download these drivers here: http://www.pny.com/support/drivers/?prod=sSlot