Hello im new here so please go easy.

Well i am a very strong lover of XP but with the new games and graphics cards coming out i see how xp is going to be out of the loop of direct x and the best gaming experience so i bought windows 7 havent installed it yet tho. i have a few questions when ever i had a crash on my computer for what ever reason i could just use the ctrl f11 to boot back to factory if i do a clean install will that partition be removed and i was not given OS CDs so in case i dont like windows 7 i would like to go back to my old OS and yes i know about windows.old but i would like for my partition to be there its been more reliable for me thank you in advance sorry if i sound a little noobish with this my first jump to a new OS in a LONG time