Last month I wrote about replacing Calc with CalcPlus. If you'd really like to keep the default calculator around, I've stumbled across another fix for the problem. This involves editing the registry, so the standard disclaimers apply.
Recall root of the Calc problem is that it stores its settings in the SciCalc section of win.ini. In order to fix that, we can take advantage of Window's ability to remap ini file accesses to the registry. Specifically, for calc, you'll need to create a key under:
The key should be named SciCalc and have a value of: USR:Software\\Microsoft\\Calc
For those playing along at home, a .reg file to do this would be: