Microsoft has announced that a beta version of their upcoming free antivirus software, MSE appears to be pretty lightweight and has modest system requirements. Installed, it consumes about 11MB of space and requests that 140MB of additional hard drive space is available. For XP users it is recommended to have a CPU with a clock speed of at least 500MHz and a minimum of 256MB of RAM. Vista and 7 users are suggested to have a 1GHz CPU and 1GB of RAM.