Hello Plet L. Welcome to the Forum.
If you buy a "modern" parallel port card that has
drivers specifically for Windows 7 you should be good to print.
But a quick look on the web shows people having problems getting the scanner to work in Windows 7. It looks like the workaround was to use a virtual XP machine to do so.
If the printer is installed and working on the Windows 7 computer then the laptop should still be able to use it through the Wireless LAN as the negotiation is between the PC's, not the printer. The only glitch would be if the XP's
driver would need to be updated to use the printer through the desktop's parallel port card.
IMHO- This is something you try - set a maximum amount of time and money that you find reasonable - and if you can't get it to work by then you just need to bite the bullet and buy a new printer.