As whs said, you definitely want to read that thread and the link posted about halfway into it as well. Also, you may want to also go over the "Things to try" section of this KB article
. Unless you changed something else recently, though, it doesn't make sense that the BIOS has started reserving more memory than it did previously. Some of the people who managed to fix their i7+RAM issues in the previously-linked threads found it was indeed issues with RAM at the wrong speeds, overclocking, or configuring Windows max CPU setting (avoiding some of the BIOS checks at boot).