Windows 7: Windows XP/7 Printer and Folder Sharing Don't Work

My system:



Windows XP SP2+ HP desktop
Windows 7 Home Premium 64-bit Toshiba laptop
HP 2610 Photosmart printer connected via Ethernet
Linksys router

The printer has worked uneventfully for years with my HP desktop.
Windows 7 was able to add the printer (and maybe download a new
driver) without any additional prompting from me. When I try to print
a document from the Sumatra PDF reader, I can see the printer and
choose it. (In fact, I made it the default printer on the laptop).
However, when I try to print, the document goes into the print
queue and just sits there forever. No status is listed for the document
in the queue. If I try to restart it, the same thing happens again.
I just put new ink cartridges in the printer and have cycled it on
and off again, but that didn't help. When I first added the printer
from my laptop, I was able to successfully print the test page.
Why won't it process the print queue now?

For the record, each machine can ping the other as well as the
printer, so the network connection itself is good. The router
can certainly see the IP addresses of all three machines.

I also had an earlier issue where I tried to created a shared
folder under Windows 7 (not using a Homegroup), but the XP
machine couldn't find it. The actual error message is

Windows cannot find \\MACHINE_NAME\path\to\folder.
Make sure you typed the name correctly, and then
try again. To search for a file, click the Start button,
and then click Search.

I note that the XP machine's workgroup was named
'MY_LAN,' but I changed it to 'WORKGROUP' to match
my Windows 7 machine. I think when I added the
printer under Windows 7, the old workgroup name was
still in effect on the XP machine, if that makes a difference.
The folder sharing was attempted AFTER I changed the
workgroup name on the XP machine. Any ideas?