What you may want to try is deleting everything related to MB off your computer. Then, copy the files MB needs to run into a folder, and tell ReAct to install into that folder. That usually does the trick for me.
Note also that ReAct is a very unstable game by nature, but you can reduce the crash frequency by doing the following:
1. Changing your regional settings to Japanese in control panel. Seriously, this isn't as bad as it sounds, and your Japanese programs will have less issues.
2. Getting the latest patch (2.007) from Watanabe Seisakujou's site:
3. Playing the game in full screen. For some reason, it seems to crash less that way for me.