Have windows 7 ult, but have win 7 prem CD, want to wipe/reinst Win7

I bought an Alienware m17x on ebay about 6 months ago

seller wiped and reinstalled windows before selling

I would like to wipe and reinstall now

I have been prepping with this thread:
http://www.sevenforums.com/installation-setup/97732-erase-hard-drive-reinstall-windows.html

when i started collecting my tools together, i noticed that the disk that came with the laptop says Windows 7 home premium, but i have Ultimate installed on the computer (before i got it)... i did find a Ultimate Key in a saved file in Documents.

so my question is. when i wipe and re install, do i use the Prem CD and then maybe log on to Microsoft site and down load Ultimate upgrade using the key i have been given with the computer?

Also, i have dual HDD in what i believe to be a RAID1 set up, is this to involved for a install noob to over take, should i or could i, send it back to Dell/Alienware and have them wipe/reinstall

thank you for any response. i hope to help someone on this forum one day. seems like a nice place

Look on the bottom of laptop or under battery to see what the licensed version is on the COA sticker. If the Product Key is readable I would use it with the installer provided here to Clean Reinstall - Factory OEM Windows 7.

Of course you can try installing Ultimate if you think the seller really gave you a legit key for an expensive version of Window 7. But the vast majority of users dont need the extra expensive features so I'd stick with the licensed version that came with the rig if not: Compare Windows 7 Editions - Windows 7 Forums

There are special Notes in the tutorial for Dell owners to read. Look for the Factory Recovery and Diagnostics Tools partitions to see if they're still there and will run. If not then during booted install you can delete all partitions and create new as you wish to get the cleanest install.

Only if there are install problems should you unRAID the HD's and change to AHCI mode in BIOS setup. We can help you further then if its necessary. If install fails it may only require wiping the HD with Diskpart Clean Command.