Legally the key was put on a sticker at the bottom of your Studio 1558 and is licensed only for that laptop.  If you still had the key, could you have transferred it to your 'new' computer? technically yes, but with Microsoft's EULA changing all the time I don't know if its 'legal'  I had a key that was on an older computer and I transferred it to a newer computer when the old one died and everything was fine.  The Microsoft Police didn't arrest me or anything.    Long story short anyway, the biggest problem is if you trashed the laptop with the key on it there is no way to recover it.
first time posting so please bear with me. my Dell Studio 1558 running windows-7 recently died.  the motherboard somehow got fried.  i pulled the hard-drive out and recycled the laptop.  a friend gave me his old dell inspiron (running Vista).  it's slow and freezes up alot when surfing the internet.   i recently remembered i have a "Reinstallation DVD" for windows-7 that came with my (now dead) Studio 1558.   i was wondering if i can (legally) replace Vista with Windows-7?  i want to do a clean install, wipe everything off the Inspiron laptop and load Windows-7.   I ran a diagnostic and the Inspiron can run Windows-7. i presume if i try installing windows-7, i would get prompted for some sort of activiation key (which i don't have).  since my old laptop is dead and gone, is there someone or someplace i can reach out to where they can give me the activation key since i will really only be running one version of the OS? one last note: i still have the old hard drive from the dead studio 1558 - could i leverage that somehow?  hope i posted this in the correct forum, thanks LouNYC
Installing Windows-7 on second laptop