Some corrections needed. Beginning from the 64-bit Vista, the kernel only loads drivers that are signed by a Code Signing Certificate. No WHQL certification/signing is necessary. One can buy a Code Signing Certificate starting from $160/year and the 64-bit Windows Server operating systems load his/her driver instantly. To verify driver stability Microsoft provided the Driver Verifier tool from Windows XP (i think). That makes stabilization easier. The WHQL is for those who want to make sure that the driver is compatible with one or more windows OS. They submit their own driver to Microsoft to test it on one or more Windows OS versions for about $700/OS version and platform AFAIK. If the stability tests passed Microsoft sends back a WHQL signed version of the driver.

BACKUP before upgrading.

Not to mention that before every upgrade one should make a backup of the whole system.

I share the opinion that linux performs remarkably better on older hardware. But older hardware doesn't mean it's power consumption is lower. (I mean typical desktop computers @ companies, not high-end PC-s.) Older processors had greater power needs for example. Plus I'm not sure older hardware has been made of more environmental friendly materials than the most recent devices. [Sorry for my english.]