Can two identical Windows computers produce different calculations?

Yes, two computers with the same hardware and software can sometimes produce different results, although this should not normally happen for a deterministic calculation.

The difference may come from several things, such as different CPU behavior, compiler settings, floating-point calculations, different drivers, system updates, or even hardware problems. If the calculation uses multiple CPU cores or threads, the order of operations can also affect the final result, especially with floating-point numbers.

I use Linux, but the same general idea applies here. I would first make sure both machines are running exactly the same version of the software, using the same input data and settings. Then I would run the calculation several times on both computers and compare the results.

If one computer consistently gives a different result, I would check the RAM, CPU stability, temperatures, and storage, and also look for any software or configuration differences.