Can I reinstall Snow Leopard over El Capitan?

Sure, but you will likely lose all your data if you use Time Machine as it won't restore to an earlier version of OS X. I'd make a clone of your HD and then you can at least copy your data files back. You will need another EHD and either SuperDuper! or Carbon Copy Cloner to make the clone.

However rather than going backwards I'd recommend the following so we can look to see if there is anything obviously wrong with your system.

Please post an EtreCheckreport of your system. We can then look for obvious issues. Please click the link, download the app and run the report. Once you have the report, please copy and paste it as your reply to this post.

If you end up deciding to reinstalling Snow Leopard, you can use the last most “up to date” Mozilla Firefox ESR 45.9 for that version of the Mac OS. The last version is almost a year old, but, at least, it is much newer and more up to date than that very old version of Safari for OS X 10.6 Snow Leopard.

Found here.

Firefox 45.9 ESR .dmg install file here.

https://ftp.mozilla.org/pub/firefox/releases/45.9.0esr/mac/en-US/

Dbl click to download, locate the Firefox 45.9 ESR.dmg on your Mac.

Dbl click on the file and it should put up both a disk drive looking image and a pop up installation window.

Drag the Firefox Application icon into the Application folder shortcut icon in the same install window.

The go to your Applications folder, find Firefox, the launch it!

You may need to update Adobe Flash Player to the last compatible version for Firefox 45.9

You need to use Adobe's Flash Player uninstaller, first, to uninstall the older Adobe Flash Player.

https://helpx.adobe.com/flash-player/kb/uninstall-flash-player-mac-os.html

On the Adobe Flash Player section of the Adobe website, you will need to look for the last Adobe Flash Player version compatible with Mozilla Firefox 45.9.

This is the Adobe Flash Player you are looking for on the Adobe web site.

Adobe Shockwave Flash version 26.0.0.137

Look toward the bottom half of this webpage link.

https://fpdownload.macromedia.com/pub/flashplayer/installers/archive/fp_26.0.0.1 31_archive.zip

Once downloaded on your Mac, dbl-click to open the zIp file

Dbl click to Install the Mac OS version if there is one listed in the archive file (might be a .dmg file).

When you open that Adobe Flash Player archive file, it will create an archive folder.

Dbl click that folder, two other folders will appear.

Click the first folder WITHOUT THE words debug in it!

When that folder opens you are looking for a Mac OS .dmg file with this name

flashplayer26_0r0_131_mac.dmg

Dbl click on this and begin the install procedure from the brownish red Adobe install folder that appears.

Also, FYI,

On older, unsupported OS X versions, you CAN still access and get at your DropBox files from the DropBox website instead.

DropBox dropped support for their desktop widget for older OS X versions UP to OS X 10.8 Mountain Lion, which I still use fairly regularly use.

I access and get my files from accessing my account directly from the DropBox website, bookmarked on another uo to date third party web browser for OS X 10.8 Mountain Lion, in addition, to creating a shortcut to the website on my desktop. Not as convenient as DropBox’s menu widget, but it works.

Good Luck to You!

Jolane Wiegand wrote:

I have a 2009 IMac. I installed El Capitan so that I could continue using Dropbox on my desktop. It's unbearably slow now. And today I tried to upload photos and I can't get it to work. I want my IPhotos back along with Snow Leopard. I have the install disks.

FYI,

You'll have other issues reinstalling OS X 10.6 Snow Leopard on your Mac, since you didn’t clone your previous system before upgrading to El Capitán.

The version of OS X 10.6 Snow Leopard on the install discs will NOT be OS X 10.6.8, but an earlier version.

So, you will have to update that installed disc version back to OS X 10.6.8.

You have to reinstall all OS X 10.6 security updates.

Get back your most recent and compatible versions of all of your iLife/iWork apps (this may entail purchasing the proper iLife and iWork disc packages, if you hadn’t purchased these before).

You may or may not have to reinstall some of your third party apps and maybe seek out Snow Leopard updates for those apps, which may prove difficult to find now, as Snow Leopard is almost a 10 year old Mac OS.

You will have a WHOLE LOTTA work ahead of you trying to get your Snow Leopard system back to what you, originally, had before you just decided to arbitrarily upgrade to El Capitán without having any external cloned system backup of your previous system.

You may have to just think about just staying with OS X 10.11.6 El Cap, at this stage.

Once Again, Good Luck to You!