Reinstalling Dell Vista Desktop Computer?

I’m having this error

“missing file ntoskrnl.exe”

I can’t even access the recovery drive, and I know it’s most likely from that SP1 install,

But searching I found this
http://www.bleepingcomputer.com/tutorials/tutorial148.html
and I tried, It goes to the install screen, which I do have on my computer, the other drive.

I have some questions.

I reinstalled dell vista before and I needed another disc for it, cause the process takes to parts…
anybody know what that disc is?

also, It asks for my product key?
can I install my modem, get n the internet and download
this to find my key?

http://pcsupport.about.com/od/tipstricks/ht/findvistakey.htm

Please help me.