It is tricky, but
download the drivers for your parallel port scanner and install both the Win 9x and the NT version.
Install an Umax 600 p under the system control / media.
Now you have to have a boot disk from Win 9x or the bootable CD.
In the win directory / system32 /drivers you delete the umaxpcls.sys copy the sys file into it of your scanner (e.g. ab306p.sys / it is the above driver)
and rename it to umaxpcls.sys.
Restart the machine.
I hope you see it works fine.