Valve wasn't joking when it warned that the initial beta version of its living room-friendly SteamOS operating system was for experts only. The initial build was... rough, to say the least--only Nvidia graphics cards were supported, crucial dual-booting and partioning features weren't supported, and you needed a relatively new rig that rocked UEFI, rather than BIOS, to even try it out.
In the weeks since, those limitations have been falling one-by-one. Before CES, Valve updated the SteamOS beta to support Intel and AMD graphics as well as Nvidia. Over the weekend, another SteamOS beta update added BIOS support and dual-boot and custom partitioning capabilities to the operating system, with help from the Ye Olde SteamOSe team that initially provided a BIOS-ready SteamOS fork. Yay! You don't have to dedicate a whole drive to SteamOS or blow away Windows anymore!
The new dual-boot options can be found in SteamOS's "Expert Install" options, but Valve engineer John Vert strongly warns there has been very little testing conducted on this build, especially on dual-boot setups. So while running Windows alongside SteamOS should theoretically work, your mileage may vary. If you're brave enough to give dual-booting a go, be sure to back up your primary OS install and any critical information in case something goes wrong and your drive is wiped clean.
And if the whole ordeal still sounds like a bit too much of a hassle, check out the slew of Steam Machines that PC builders plan to release later this year, after Valve puts the finishing touches on SteamOS.