Can you be more specific? Where are you seeing "Can't load XPCOM"?

hello KatSaavedra, please try a clean reinstall:

• download the full firefox setup file from https://www.mozilla.org/firefox/all/
• uninstall firefox on the machine (but don't chose to delete your custom files & settings in the uninstaller)
• manually delete all remaining files in the firefox program folder, which usually resides in C:\Program Files (x86)\Mozilla Firefox\
• reinstall firefox

Duplicate to https://support.mozilla.org/en-US/questions/972465