Which version of Joomla are you using? Also, have you changed any of the parameters for the component? By default, the installation files should be listed under the ignored section of files, unless the "Ignore Regular Expression" parameter is altered.
I've changed nothing - a straight install on Joomla 1.7.3 and the ignore regular expression is still this:
Ahh.... further investigation... although I didn't change any of the paameters, once I opened the options and saved them, it's working fine. How odd!