Microsoft's attempt to copy PDF - it's a portable document format. However the only thing I've ever seen that generate it at all is Office, and I've never seen a file of that format 'in the wild', so I think we can consider it a dismal failure.
Start up task manager and switch to the 'performance' tab, then print something from another program. See what happens to the '% memory used' counter. My first guess is the Windows driver is doing ' raw print rendering' i.e. generating an image of the page at printer res, which is chewing up an awful lot of RAM and causing the PC to have to dump a lot of stuff to scratch before passing the page to the print spooler. With the Mac it might be sending the printer raw PCL, which the PC won't have to render and thus can send straight through.
If that does appear to be what's happening, see if you can tweak any settings on the printer - even to the point of sending postscript rather than PCL if you have to.
Jon