Run Windows 7 from a Seagate FreeAgent External USB Hard Drive.

Is it possible to load Windows 7 onto a Seagate FreeAgent external HD USB connect and use it on my imac? I don't use windows that much but I do have some programs from my work that is only compatible with windows. I do not necessarily want to put Windows on my iMac no more than I would use it. Thank you for any info you might share on this.