InfoWorld have a petition you can sign to ask Microsoft not to discontinue Windows XP on June 30 this year. More details can be found here.
In many respects, Vista is like the Windows
Millennium Edition that was meant to replace Windows 98 in 2000 but
caused more trouble than it was worth. At that time, Windows 2000 was
promising but didn't support a lot of hardware, so users were stuck
between two bad choices. Without admitting Millennium's failure,
Microsoft quietly put Windows 98 back on the market until the fixed
version of Windows 2000 (SP1) was available. Microsoft needs to do
something like that again today.