how to install windows 8 while having ubuntu11.10

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http://askubuntu.com – I have dell inspiron laptop with ubuntu 11.10. I have DVD of windows 8 and product key, what I want , is to install both windows 8 and keeping ubuntu 11.10 as well. So what should I do for that such booting speed doesn't goes down.(laptop with 4 GB RAM & 500 GB HDD). can u please also tell me how to upgrade ubuntu 11.10 to ubuntu 12.10 Should I delete ubuntu11.10 for installing windows 8 and then again install ubuntu.? (HowTos)