If you're still using Windows XP, you just won $100 from Microsoft.

The only catch is that you have to upgrade to a new Windows 8 computer.

Those who are eligible for the promotion can redeem the credit at Microsoft's online store or their retail shops -- and the fact that you still use the 13-year old Windows XP is subject to verification by Microsoft (MSFT). The offer is good for PCs ranging in price from $599 and $2,299 and will run until June 15.

The promotion is part of Microsoft's plan to get the last remaining Windows XP users off the operating system before the April 8 end of life date. After April 8, Microsoft will no longer issue security updates to address viruses and exploits to the operating system.

Related: Microsoft is about to take Windows XP off life support

The latest figures from NetMarketShare still show Windows XP pulling 30% of Windows users, though the vast majority of those are thought to be PCs from China and the enterprise space.

Windows 8 meanwhile, has recently moved past 10% market share amongst Windows users.