I just received my refurb MP, a stock 2.66 Xeon with 250GB drive. While waiting for it to warm up enough to plug in, I opened the case to check for freebies. In the lower RAM card, there is a single 512MB RAM module. The upper card has the normal two 512MB modules. I've read a lot of threads here but haven't seen anyone post about this. So is this safe to run as is? I assume so since they supposedly test them during the refurb process. Will it slow the machine down to run it this way? Can I order up a single 512MB stick of Apple's FB-DIMMs to complete the set?