A little follow-up. Just to make sure that this problem didn't have anything to do with trying to install on a SSD, I tried again. This time I tried installing to the L: drive, which is on the same physical hard disk as the F: drive where the setup file is located. The L: drive has over 400 GB of space. Same error - "you don't have sufficient disk space" and it erased the folder I put on L:.

And, in case this has any bearing, the hard disk where the F: drive is located is actually two identical 1TB drives configured as RAID 1.

Do you need Administrator privileges to write to those drives?

It is possible that running the Firefox setup program with elevated privileges or as Administrator is not sufficient to have write access to that drive, but that you can only do that as Administrator.

If that were true and elevated privileges were needed to write to either of those drives, then how was it able to DELETE the folder?

Are you aware that even when you install Firefox to a non-default location, such as a different logical drive, that that bulk of Firefox files are going to end up on the OS root drive in %APPDATA%\Mozilla\Firefox\Profiles\ ??

Are you aware that even when you install Firefox . . .

Yes. And then after I do the basic install, I will run the process to respecify where the profile(s) are located (just like I do on my old computer). I'll probably also move the caching off the SSD as well. Then restart Firefox and clean up the old files.

But I've never understood why developers are bound and determined to put files where *THEY* want to put them, instead of letting the customer decide.

Just wanted to make sure you were aware of that. I have a similar setup. Other than my "default" installation of Firefox, all my Profiles are located on my D:\ (data) drive. None of those Profiles even appear in the profiles.ini file, I launch everyone of them directly from the Target line for their respective shortcuts. I also move the cache for my most used Profiles, to a tiny partition that I also use for my Windows TEMP files, to cut down on de-frag time on the C:\ drive where XP is installed.

Many programs that I have used over the years use that folderset for their data files, following the lead of the way Microsoft does things, for consistency with the host operating system I suppose. I have seen a few Bugs for changing certain prefs in Firefox, and the filer of those Bugs mentioned "consistent with Microsoft Windows" and the expectations / needs of Sys Admin's for large scale network installations of Firefox.

Two Gecko browsers that keep all their files in the Program Files folderset are Firefox Portable and K-Meleon. Every other "Mozilla powered" browser I have tried does it the same way Firefox does, which came about from the original Mozilla Suite (now known as SeMonkey).

As another test, I have a copy of the Setup program for Firefox 3.5.2 (downloaded Aug 12, 2009). The exact same thing happens.

I've already searched Google to see if anyone had a similar problem installing any other application - nada. And since this is basically a virgin PC, I can't believe it is anything involving my Windows 7 settings. Plus since the same problem occurs when trying to install to either the SSD or the hard drive, that rules out something wrong with the SSD (I've since installed other files and applications on it OK).

Thank god my (day job) work computer had an even older Setup file on it: Ver 3.0.4 which I had downloaded on Dec 12, 2008.

I transferred that over via a USB flash drive and ... SUCCESS!

Now that I have Firefox installed, I can then do the automatic upgrade to 3.6.12.

So ... what was done between at least 3.0.4 to 3.5.2 that prevents Firefox from recognizing the proper amount of free space available, and then also goes ahead and deletes the folder where I wanted it installed?

And in case you're wondering, yes, all of my drives/disks are formatted NTFS.

SUGGESTION: Unless I missed it somewhere, could older Setup files be made available for situations such as mine? I don't mean every iteration - maybe just the first one of each major change (3.0, 3.1, 3.2, etc). That way when people have problems, they can go backwards one step at a time to see if that corrects their particular problem. Obviously if it works, they can then do the normal upgrade to get up to the current level.

Every version of Firefox that was ever released is available from Mozilla, you just need to know where to look.

ftp://ftp.mozilla.org/pub/firefox/releases/

"the-edmeister": Thanks. That list of previous versions wasn't clearly found on any of the screens/pages. I did eventually find the pointing to the FTP page by searching on the term "previous versions" then scrolling around a bit.

Since I haven't customized my system yet, I'll uninstall 3.0.4 and play around to see if I can identify when things went south.

I did a little more testing to narrow things down. 3.0 RC 3 worked; 3.5 failed. So that's when things changed. (I didn't try the 3.1 betas)