You may have already seen the various announcements posted on the ECE site or on the old OEM secure site in November regarding SP1 support ending in April 2007. To review the announcement, visit the ECE link above, and navigate to Communications > View All Communications, then select 2006 on the right, and view the November 2006 announcements to find the following, posted on November 10, 2006:
Support Lifecycle for Microsoft Windows XP Embedded and Microsoft Windows Embedded for Point of Service - Announcement
There are two announcements, one posted for OEMs who purchase through distribution, and the other for Direct OEMs.
To summarize, under Microsoft Support Lifecycle Policy, Microsoft® Windows® XP Embedded SP1 support is available for at least one year after the successor Service Pack is released. XPe SP2 was released on 18 January 2005, so the end date for support of SP1 will, be, in effect, just over 2 years from that date, namely 10 April 2007. For more details on Product Lifecycle Support see the Support Lifecycle site - specifics for XP Embedded are listed at this link - scroll down to Windows Embedded.