Firstly, what version are you running on now? Go to Settings>About phone>Software information
If it's 2.09.405.8 you can either get the OTA update (Settings>About phone>System software updates) or get the full RUU file (which will reset your phone) form here:
Shipped ROMs
The RUU you want is this:
RUU_Bravo_Froyo_HTC_WWE_2.10.405.2_R_Radio_32.44.00.32U_5.09.05.30_2_release_142828_signed.exe
If going down the RUU route, you'll need your phone to be connected with HTC Sync and then just run the file