The problem of slow booting is also fixed by installing a graphics card, so it appears it's being caused in some way by the onboard intel graphics. Using the internal graphics I found that to get the maximum memory possible without slowing the system to a crawl, ~3781MB (as reported by free -m), in CentOS/Red Hat 5 I had to set mem=4700M as a boot parameter (Despite only having 4GB ram). Whatever...