At least Dell provide OS discs with their PCs I know HP do also, but some manufacturers don't provide any discs (e.g. some Acer computers I've set up for people). So for anyone else here planning on doing a complete reinstall, make sure you have the operating system disc and discs for any applications installed (e.g. DVD player, CD/DVD burning software. etc.) handy before reinstalling. Some PCs which do not include any recovery discs give the option to burn restore discs, so it's vital this is carried out before it's too late (e.g. HDD crash :doh: ).
If your Dell PC has both restore discs and the Windows OS disc and you are familiar with installing drivers, software, etc., I would recommend using the OS disc to reinstall Windows and then installing the drivers one by one. You can get the latest drivers from Dell's website. Just go into "Support -> Drivers & Downloads" and following the steps. I usually find this a great way of getting extra performance out of a PC/laptop, as you only install the software you're interested in With a new laptop or even restoring using the system restore discs, there is usually quite a lot of (often unused) software that is put on the PC, which can slow the system down and uninstalling unneeded software does not always help much.
The main drivers to make sure you have handy before formatting include: Wired / Wireless network driver and the display driver. The network driver is important as you'll need this to get back online after a reinstall if Windows doesn't have a native driver for the network card. Once you're online, you can download any missing drivers if you end up with a missing disc.
After you've the drivers & applications on, you can install the software one by one. As far as I'm aware of, Dell includes all the individual software discs for any applications that were bundled with the PC. Of course, just install the ones you plan using. Finally, watch out for Windows updates and be careful with what websites you browse until all the updates have finished downloading and been applied.