Do you install your OS first or is there something else on your mind?
Yep... literally the first thing I do. Fire up a Linux liveCD to partition my drives, and then copy over my old Linux install. Then I install Windows, and then reboot and set up the boot loader in Linux.
Do you begin by tweaking the BIOS to your liking or leave all that until later?
I do some mild tweaking, such as disabling onboard sound card, serial port and other ports I don't use, and set up RAM to factory settings, but I don't do any actual overclocking before I've set it all up.
Do you use the drivers on the disc provided with the hardware or go straight to the manufacturers website?
Unless the network card isn't supported in Windows (it usually is since I try to aim for Intel network cards), I try to get them from the manufacturers site.
Do you tweak anything specific once in the OS that you just can't live without, a special theme, remove unwanted bloat?
I always disable mouse acceleration - MarkC's mouse fix works best I've found out. I usually install WinRAR, but I've started to use 7Zip more and more here on the latest..
Do you have to get that CPU overclocked before you bother with anything else?
Not before I've set my OS up completely.
For my desktop computer I usually install these on the first day (excluding drivers):
- Visual Studio
- PuTTy + set up Pageant
- WinRAR or 7Zip (more and more often I use 7Zip because of the licensing issues with WinRAR)
- Different games (Steam + most commonly played games; CS:S and CS 1.6, WoW, Heroes of Newerth)