Because POSUSB driver disappears from Microsoft site, here you are :-)
[However, I don't recommend it for serious application. The code is buggy and slow (<= 64kBytes/s ??), but it works somehow.]
Are you using WIN98SE and want to use USBCheck tool? Here is the old version (5.00 Beta), which works well on WIN98SE for me.
And here is even older version (3.5)
Note: New version of USBCheck can be found at www.usb.org.