Is Acrobat Pro XI compatible with Windows XP?

I have one old XP-SP3 system; Acrobat XI works very nicely on it.

yes:

• 1.3GHz  or faster processor
• Microsoft Windows XP with Service Pack 3 for 32 bit or Service Pack 2 for 64 bit; Windows Server 2003 R2 (32 bit and 64 bit); Windows Server 2008 or 2008 R2 (32 bit and 64 bit); Windows 7 (32 bit and 64 bit); or Windows 8 (32 bit and 64 bit)
• 512MB of RAM (1GB recommended)
• 1.85GB of available hard-disk space
• 1024x768 screen resolution
• DVD-ROM drive
• Internet Explorer 7, 8, 9, or 10; Firefox Extended Support Release; or Chrome
• Video hardware acceleration (optional)