Hey there, @faizan2508.
Your computer needs specific compatibility requirements to run QuickBooks Desktop smoothly. Since you installed the product on a new computer, your operating system, hardware, software, and other requirements may be unsupported. This can be the reason why you're unable to use the multi-user mode feature.
I suggest using a compatible computer for the QuickBooks Desktop 2011 Pro version. You can reach out to an IT specialist to help check your computer specs and run the program. They can guide you on what to do with your system to meet all the requirements.
You might also consider reading this handy article that will discuss more details about access limits in single or multi-user mode: Tasks that can be performed in a single or multi-user mode in QuickBooks Desktop.
Please let me know if you need further assistance installing the product and using the multi-user mode feature. We'll be here to help. Have a good one.
