1. You will need a real deal Dell 7 OEM disc if you want auto activation via the Dell 7 SLIC, assuming it has one,
2. otherwise if using just a generic 7 OEM disc, use the COA sticker key stuck somewhere on the laptop, install... then phone MS or activate online
3. If you're lucky there may be a hidden recovery partition on the Dell and you can do a clean install and instant activation with that,
no disc required, and no driver headaches
All the above are legit methods IIRC, so no door knocks, suits, and helicoptors hovering overhead to worry about at 6 am
Usually you can't go wrong with a Dell laptop,
batteries can be a coin toss sometimes, like all the brands