The last 600 Megabytes comes hard.

I have been cleaning up the hard drive on AntiqueLaptop.  I gave this HP laptop to youngest son when he was in high school.  Since then youngest son has graduated college, and the high school laptop wasn't cool enough for him, so it came back to me.  It has plenty of punch to run all my programs, and  I can sit on the deck in summer and web surf with it.  When I got it back, the 40 Gig hard drive was full.
    Some obvious weeding of music and games, followed by passes with CCleaner, turning off System Restore freed up 10 Gigs or so, enough to install M$ Visual C, all my digital photos, all my back email, lotta stuff.
    Then I ran Windirstat.  That showed me 2.7 Gigs of  recycle bin files that the recycle bin didn't see and would not flush.  Some how a second Recycler directory had taken root in Program Files.  That's not supposed to happen, but with Windows all things are possible.  Explorer failed to delete it.  But Windirstat has a zap files feature that did 'em  just fine.   

Then I found that  hidden system C:\Windows\Installer directory had grown to 1.6 Gigabytes.  A real diskhog on a 40 Gig laptop.  I was able to recover 0.6 Gigabytes with Microsoft program MSIZAP.exe.  The Installer directory is a space waster invented to support uninstallation of Office.  It contains hundreds of fat files with random number names.  Some (but not all) files are obsolete, they belong to old products previously removed from the system, except the uninstaller leaves the fat files behind.  The MSIZAP.exe program is a DOS program that with command line switches ! and G will delete any files in the installer directory that are not referenced in the registry. 

Step 1 is to obtain MSIZAP.  This is non trivial because Microsoft has withdrawn it.  Apparently Windows 7 and 8 are less robust than XP, and MSIZAP was breaking something in the "new and improved" Windows versions..  I am still running trusty XP, so I don’t care about breaking Win 7  and 8.   Despite the M$ down check, the program is so useful that private websites still have it.     I found it at: http://majorgeeks.com/downloadget.php?id=4459&file=15&evp=fe1c76da3437592326a3d668d72bf8f5  under the name “msicuu2.exe”  Actually msicuu2 is a fancier M$ installer cleaner upper.  The fancier part calls good old msizap to get the work done.  After downloading and installing the msicuu2 package you will find msizap.exe in the newly created Program Files/ Windows Installer Clean Up directory. 

Step 2 is to run it.  Do Start -> Run and then open a dos window by typing “Cmd.com” in the run box.  Use the DOS  CD command to set the current directory to c:Program File\ Windows Installer Clean Up.  Remember to inclose directory names containing spaces in double quote marks.  Such as

CD c:\”program files”

Followed by

CD “windows installer clean up”  to avoid typing a long filestring in one fell swoop. 

Then execute msizap with the following command line

Msizap !G 

Be sure to include the !G command line switches, otherwise the program may do bad things.  On my machine the msizap issued a couple of “Error 2”  messages and then reported removing about 20 files. 

Checking afterwards showed the Windows Installer directory had shrunk from 1.6 Gig down to 1 Gig. 

  That's a lot of work for a measly 600 Meg.  BTW,  I read a lot of web chit chat to the effect that MSIZAP does bad things to Win 7 and 8, and newer versions of Office so beware.