One thing you must know is that even though you can use the latest browsers to surf the net and so on so forth, you cannot use it to test using the SilkTest tool. This really sucks. Many a time, I tried using the latest versions of firefox and ie to test, but simply was left with a command line instead of browser test framework. First of all to start testing, if you are using Silktest 2008, try using Mozilla 2.0 and IE 7.IE sucks so lets go with firefox 2.0. The two places where you will have to set the extensions are for silktest to recognize the browser are:
1) start-> All Programs-> Borland-> Silktest-> Extension Enabler.
If you dont set this there might be problems in running you tests. This is the global settings for Silktest.
2) Project specific settings-> Select a project. Goto options->Extensions in the silktest windows. In the ensuing window select the extensions you would like to enable. These settings are for the project specific ones. Any questions send me a message. Goodluck.