OKLAHOMA CITY - Tuesday marks the end of an era for 300 million computer users who use the "Windows XP" operating system.

Windows XP is installed in almost a third of the computers there are in the world, according to Best Buy.

Bill Hammond is the sales manager of Best Buy's location on May in Oklahoma City. He said beginning Tuesday, Microsoft will no longer be offering updates for Windows XP.

Hammond said what that means is without updates, Windows XP will no longer be compatible to some computers, and because of that, it can present security and other problems.

To avoid that, Best Buy is offering a computer upgrade program to continue to insure compatibility. The cost ranges from $100 to $120.

Hammond said Best Buy is also offering a $100 credit to customers who trade in their old computer and buy a new one.

"I think it's a personal choice for the customer to make, but if they come on in we'd love to help them make that choice," Hammond said.