When the script doesn't work as you think it should, it's usually helpful to print the contents of some variables to see whether they contain the data you think they do!

$unInstallExepath= "c:\program files\netbeans 7.0\uninstall.exe";
print $unInstallExepath, "\n";
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Does this print what you thought it will? Try to find out why!

Then try to print what you pass to the chdir() function:

print '$path', "\n";
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Again not what you seem to expect. Remember, the quotes matter!