It says that it will install the stuff in 3 secs. When it does, do a soft reset. This will cancel the install. If you go into the File Explorer, you will see a storage card call "Extended_ROM". Inside is the stuff installed normally at the beginning. I selected to install the PhonePad (a big keyed, T9 Predictive text input pad) and the operator settings for my provider (Optus Australia). I also installed Caller ID, but it really isn't necessary and can save you a bit extra RAM. They are named.
By installing these three things, I have saved about 15mb on my internal memory. I used to have 25-27mb in use, now i have only 10mb in use with all the stuff I used to have installed! It has made my device much faster and I haven't got a single low memory error since. I have found this a much better option, and may save some from needing the 128Mb RAM upgrade (but it still would be nice , just can't afford ).