In Linux, you can see your whole 8 GB of RAM even if you have a 32 bit OS. Memory reserved for a single program is reserved to little under 4 GB, which is rarely a problem.
See screenshot from Ubuntu 11.04 Natty on a HP-Compaq 8200 with 8 GB of RAM. ‘uname -m’ shows I’m running 32-bit (because it doesn’t say “…64…”). ‘free -m’ shows Linux can see about 8 GB of memory.