No, disabling SSDP and UPnP won't screw anything up. As a matter of fact, disabling both of those services is highly recommended as both are security holes when running.
If you had those two enabled, you probably need to go to
Black Viper's site and use the chart there to disable all of XP's unnecessary services. Use the settings in the Safe column.
It's a little tedious but well worth it in terms of better system performance and increased online security.