Can you post exactly what you have done to generate that message about prefix? It will help people here help you. Basically, as I understand it with Linspire, you can either use their click-n-run method to install software (which costs money) or set up apt (see this
. You should be able to install gcc via either method. The alternative is to look for a binary (not source) package on gcc.gnu.org, download it, extract it, read the directions (there will be a README file) and install it.