How to Get Support, Post-Cutoff
Obtaining support for XP after June 30 will be easier than trying to buy XP after that date. For starters, you have access to what Microsoft calls "mainstream support" for XP until April 14, 2009. Mainstream support includes the release of bug fixes and security patches, so you'll still be receiving updates for the operating system. You can pay Microsoft for help, as well, and the company will also honor all warranty claims until then.
After that date, and until April 8, 2014, Microsoft will offer what it calls "extended support" for XP. During that time, Microsoft will continue to issue security patches but won't release public bug fixes. Businesses that signed support contracts with Microsoft will be able to get bug fixes, but no one else will. Paid support will still be available, but warranty claims won't be honored. Microsoft says Windows XP customers will have to take up such claims--even if they relate to software--with the PC manufacturer at that point.
Whether you can obtain support from your PC's manufacturer may depend on the way in which XP was installed on your system. For example, Dell will support XP on your system as long as Dell installed it--perhaps via the downgrade option--or prior to June 30. But if you bought a Windows Vista PC and then installed XP yourself, Dell won't support it.