If you own any of the following devices and you still have not upgraded to Windows Mobile 6, then you better upgrade your device(s) before Oct 31, 2008 because HTC is going to remove the free upgrades after that date.
Here is a message on the HTC’s website:
October 31st is the last day to take advantage of the free upgrade to Windows Mobile® 6. The upgrade link will be removed from HTC’s website at 12:00 pm (noon) GMT on October 31st.
Removal of this free upgrade may affect users of the following devices: HTC S621, HTC S620, HTC P4350, HTC P3300, HTC Advantage.
You can check your windows version by Start > Settings > System tab > About