Use Windows Explore.
Highlight the folder QA4.
Right click on the folder.
Left click on Rename
Change name to QA, press Enter.
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In future, make sure that path is not included in programming statements or macros.  Set default path to whatever you want on that machine.  Then when Q&A calls for path, just press SH-F4 to delete the line, press Enter, and the default path will appear.

Set the default path from the Q&A Main Menu.
Select Utilities, Set Global Options.  On the second line, enter the path you want as default. 

You could do that now, (change the default from C:\QA\ to C:\QA4\), vs. renaming the folder.  But you may have some failures if programming or macros have "hard-coded"   paths.  Right now, renaming the folder sounds like the safest option.