April 8, 2014 marks the end of Windows XP Support. According to Microsoft:

“It means you should take action. After April 8, 2014, there will be no new security updates, non-security hotfixes, free or paid assisted support options or online technical content updates.”

One of the first things you will do to address your Windows XP to Windows 8 migration is to test your current applications for compatibility to the planned new Windows client platform. I have compiled a list of the Top 10 Issues that will, and still, affect Windows 8 deployment in your organization. I used Citrix AppDNA 6.3 Application Compatibility Software to gather information based on 35 randomly selected apps that run on Windows XP. Note that I have deliberately omitted the remediation actions for most of these issues, and only included those commonly known and obvious ones.

These issues don’t just affect migration to a new Windows client platform. Companies currently on Windows XP and are deploying Citrix XenApp or Citrix XenDesktop will sooner or later encounter these issues, and more.  For XenApp 6.5, we need to ensure that the application runs on Windows Server 2008 R2 (which is 64-bit adding another layer of compatibility issues not addressed in this article), as well as have the ability to run in a remote desktop/TS capacity. For XenDesktop, we need to consider that the application should be able to run on the target Windows platform that will be used and if this platform will be 64-bit.

And here they are (full article)