Help with ROMS please?

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http://androidforums.com – Im currently running stock Rom rooted 4.1.2 with siyah 1.8.6 kernel. I would luke to put a 4.1 jelly bean htc rom on or the cm10.1 4.2.1 or any other good latest roms? The thing is I want to be able to switch to my stock rooted rom whenever I like without flashing in cwm or odin. I have also saved a backup of my device through cwm but instead on it being on the internal sdcard its saved to my extSD. Ive heard this may be a problem in cm10.1 as sometimes it wont detect an sd card. So could someone help please in showing me how to have 2 roms, my stock and a different rom that i would like to (General)