Alaikum Al Salam,
Please use Cisco Feature Navigator to find information about Cisco IOS software images and the supported features for your platform(s) :
http://tools.cisco.com/ITDIT/CFN/jsp/index.jsp
Search by feature and choose MPLS, and then choose Cisco 2801 as the platform, you'll get a list of the IOSs that support MPLS on your platform, and please always check the required DRAM and Flash.
BR,
Mohammed Mahmoud.