This is not a Firefox issue, it's more about your computer configuration. Please read the following article to see if it helps:

http://social.answers.microsoft.com/Forums/en-US/xpinstall/thread/d10378f6-5371-4676-a6ff-ab84aa584020/

Also you can google the error message and you will see lots of answers come up.

That is not a Firefox error message. It is a Windows message, administrators can set a quota for the amount of disk space a user can use.

If this is your own computer and you have administrator access, open Windows Explorer, right-click on the drive that Firefox is on (typically this will be the C drive) and select properties. Go to the Quota tab of the properties dialog and click on the "Show Quota Settings" button. Now de-select the option to "Enable quota management"