As expected, Microsoft has pushed out a mandatory update to the Xbox 360 today, which adds support for USB storage devices, expanding the memory capacity of the five-year old video game console.

The update will ostensibly allow any FAT32-formatted USB storage device between 1GB-16GB in size to be used to save profiles, game saves, and downloadable content. There are, however, a number of caveats, which mean users can’t just plug anything in and have it work.

When the update was first announced, Larry “Major Nelson” Hryb said “Since performance on flash based USB storage is usually better, I highly recommend using flash based instead of spinning media like a hard drive…it’s just going to give you a MUCH better experience.”

Microsoft has minimum performance recommendations for USB storage devices, and if the one you plug in does not meet them, you will be warned. So far, it looks like Microsoft is using this update to highlight the partnership with SanDisk on the branded Xbox 360 USB memory stick, which comes pre-configured with the software update on board, and includes a one month Gold subscription to Xbox Live.