can't share files between networked computers after downloading security patches

>-----Original Message-----
>Since setting up a wireless router, I have been able to
>share files between my DSL-connected desktop (xp home)
>and laptop (xp pro). That capability was disabled after
>I downloaded the Microsoft patches to protect against the
>Sobig and Blaster viruses in August. I can surf the Net
>from either computer but no longer share files between
>them.
>
>Apparently, the downloads changed settings relating to
>the firewall, ports, or file-sharing permission but I
>can't figure out what settings need to be changed to
>restore file-sharings. The desktop does not even detect
>the laptop on the network while the laptop detects the
>desktop but won't allow me to click on the desktop folder
>to open it.
>What to do?
>thank you,
>Ricky
>.
>