Windows installer folder, why wouldn't it change at all

I'm working with an old weary Windows Vista, I've been using it since four or five years ago, installing many different stuff and uninstalling others. Only recently I tried to tidy up a little bit my system, and I discovered this windows\installer folder, mysterious and lethal and also huge. I searched around to find if there is anything I can do to somehow cut off a bit of that, and best thing I found was Microsoft tools, different versions and names, so I used this Fix it troubleshooter, after Microsoft Installer Cleanup Utility (msicuu) crashed my computer twice, and started to remove almost anything I thought I should, and along with that, I removed tons of programs using Windows's plain old add/remove program utility. So I thought after all this I would find the installer folder a bit shrunk, but it is still exactly like the first day.

Now I'm totally disappointed and confused, I thought the contents of that folder had something to do with installing and uninstalling my programs, but it looks it's not. So I would like to know what exactly is in there and which parts I can safely delete, and maybe some hint on how to do that would be extra helpful.

P.S: I sure have already checked Is it safe to delete from C:\Windows\Installer?, It only tells me it is evil, stay awy from it; and I found How to safely delete stuff from %SystemDrive%\Windows\Installer? rather irrelevent.

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What exactly is your question? –  Ramhound Sep 22 '13 at 14:53
–  techie007 Sep 22 '13 at 15:52
@Ramhound Edited. Hope it's more clear now. –  arsaKasra Sep 22 '13 at 16:53
Yes, it is indeed related to installing programs; when you install a program using Microsoft Installer, it puts a part of the installation program in the Installer folder so that you can modify, repair, or uninstall it later (it is a better system than in the past when installers would put a file like unwise32.exe, unvise.exe, uninstall.exe, etc. in \windows or \windows\system32). It is always better to uninstall from the Add/Remove Programs applet; if you deleted the (un)installer from Installer, then you can’t remove it properly. How specifically did MSICUU crash your system? –  Synetech Sep 22 '13 at 17:03
Thank you. Last things first, every time I ran MSICUU (I can't remember if a reboot was necessary) and restarted I would boot to a bluescreen and had to run a system restore, and I don't really know about the details of the reason. And about the first part, so shouldn't uninstalling the program remove that part of the installation it put in Installer during the install? –  arsaKasra Sep 22 '13 at 17:21