To be able to remove the Thunderbolt's rockets you have to install the update first. Next, look on the 2D cockpit panel (Shift+1) and you'll see a new icon that looks like the rear view of a rocket.
As for changing the payload, the primary way is to do this in the setup menu before you start your flight. You can also bring up the Fuel and Payload window midflight if you hit the ALT key and choose the "Aircraft" option from the top of the screen. From there you can customize the overall weight of the aircraft through several individual variables. You can also affect the weight/balance of the aircraft by releasing your drop tanks (the levers are located at the bottom of the instrument panel and must be clicked twice each to arm and then release). I can't remember for certain if releasing bombs and removing rockets have an affect on your aircraft's weight but I believe that these do not and you must make the necessary weight changes in the Fuel and Payload menu. A2A Simulations' FS2004 product line
.* Note: Some1 posted while I was composing my reply, but I have some alternate links and info:
My personal recommendation is that you first look for WWII Fighters Special Edition
. I hope it is still available through A2A's online store because I think it is otherwise out of print. If you can find this product you'll essentially gain all of the SOLO download aircraft plus the Japanese A6M.
If you prefer multi-engined bombers like the B-17, look for a copy of the first Aircraft Power Pack
; this product is essentially a rerelease of Wings of Power: Heavy Bombers & Jets
for FS2004 but it also includes the update patches, some additional skins, and the SOLO version of the P-51D Mustang as a bonus. Unfortunately I believe APP is long out of print and you might only be able to get it used or from a reseller like Amazon.
_________________I like Thunderbolts!
(Link to MySpace tribute page)120th Fighter Wing, Montana Air National Guard