I short, I think so!
What you've got to understand is this... With 'serial to USB' adapters, you get a similar cable with a serial port on the end rather than parallel. You then install a driver (or maybe your OS already has one?) that creates a 'COM' port. This 'COM' port that appears in your device manager (if you're using Windows) is just like a 'real' one, so software can't tell the difference and that means almost any software can use it like a real serial port.
Now, I'm presuming that this parallel one creates an 'LPT' port so it's compatible with any software/hardware that uses a parallel port, but not having one of adapters like you've mentioned, I can't be sure.
Can anyone who owns one of these USB/Parallel shed any light?
To be honest I'd say it's pretty likely to work, but be prepared for the small chance that it doesn't-- I'd definitely say it's 100% more likely than your crazy idea in the original post
(Also, bear in mind that the driver is 99% responsible for the operation, so you're relying on software a lot!)
In the e-Bay post, there is this :
Driver CD available on request for Windows 98Se or ME users
Which shows that Windows 2000 and XP probably have drivers already, and I'd imagine the drivers function is to expose a virtual LPT port, which is what you want