I don’t think there is a major computer manufacturer today who will sell you a computer without an operating system. You’ll get the current version of Windows, or perhaps the vendor’s choice of Linux distributions, preinstalled on your computer — whether you want it or not. The manufacturers differ, though, on whether or not they give you original CDROMs of the operating system.
Some manufacturers provide you with original CDROMs. Those are the manufacturers who will get my business.
Other manufacturers take a cheaper option on Windows licensing — they pay less to Microsoft if they give you a restore CD, since you can only use it with their motherboard. If your motherboard dies in warranty, you get another one from them and all is well. If it dies outside of warranty, you buy a new motherboard from them or a new motherboard and a new copy of Windows. Might as well buy a new computer, with the pricing of a retail copy of Windows XP.
How about the other guys — the ones that don’t give you any of the above? You should get at least a recovery CDROM with any computer you buy. In that case, fixing your OS usually means blowing away everything on your computer and putting the hard drive back to the original condition…
At least one major manufacturer makes it your task — and he saves the cost of 6 to 8 CDROMs. When you first boot your new computer, it tells you that you need to make your recovery CDs. It even reminds you a few times, too. But, I think there’s one of those little “don’t tell me again” checkboxes on the warning.
If your manufacturer wants you to make the recovery CDs, you need to do it. Even though you would like to surf the web, set up your email or whatever, consider it part of the process to set up the computer.