I have an HP 4550 laser jet connected to an old windows 98 PC as it has a parallel cable. My Windows XP PC's can print to it but my win 7 PC's won't. Win 7 sees the 98 PC and sees the 4550 through the network it just won't connect.
You can try the printer sharing fix listed somewhere in the Vista forum... the same fix works for Windows 7. However, one thing you should check for is whether or not the LJ 4550 is actually compatible with Windows 7. If it is, you would be much better off sharing it from another computer.