While with a bit of hacking you can get any vendors firmware (for the same device) to work, you're best to stick with your vendor's firmware. The global list of vendor firmware links is here: BlackBerry Desktop and Device Software Download Sites
The 7230 uses the same software as the 7210 and 7280 (no hacking required - not sure what JerryD is referring to). Download the latest version - which is not particularly new and install it to your PC.