Slowness in a computer can be caused by many things, mostly a lack of free space on the hard drive or insufficient RAM for the tasks it is asked to do.
As for MacKeeper:
Do not install MacKeeper (and how to uninstall it if you have):
(Please note that references to the original developers, Zeobit, also now refer to Kromtech Alliance Corp, who acquired MacKeeper and PCKeeper from ZeoBit LLC in early 2013.)
I'm sure Klaus will come in on this too but but these are the minimum requirements to upgrade from 10.6.8 to Mavericks.
Ideally you should have at least 4GB of RAM although Apple say 2GB.
Buy the additional RAM which you can insert yourself. It is not difficult though it should be approached with care.
Before you download Mavericks (which incorporates Lion and Mountain Lion in its makeup) read the following to check if you have irreplaceable Apps that work with Snow Leopard.
Via the App store you should then be equipped to download Mavericks, but be aware it is a big program and takes time.
All good information, but I agree with Klaus. Get the system in order - for OSX 10.6.8, then upgrade. What I've gleaned so far is to
(a) check the HD free memory capacity and
(b) check that RAM is at least 2 GB for OSX 10.6, 4 GB for Mavericks - 10.9. And yes, I regularly jack up the RAM memory when buying the machines in the first place.
The present machine has been at 2 GB of RAM since purchase, and current speed is frightfully slow, compared to what it was even a year ago. Changes in user behavior/interface ? Could be. Which things are _more_ likely to slow it down?
At present, HD has 238 GB available space out of 320 GB total. Doesn't seem to be cramping up there.
So what do I look at/for, to pick up the speed a bit?
Repairing permissions is important, and should always be carried out both before and after any software installation or update.
Go to Disk Utility (this is in your Utilities Folder in your Application folder) and click on the icon of your hard disk (not the one with all the numbers).
In First Aid, click on Repair Permissions.
This only takes a minute or two in Tiger, but much longer in Later versions of OS X.
Background information here:
An article on troubleshooting Permissions can be found here:
By the way, you can ignore any messages about SUID or ACL file permissions, as explained here:
If you were having any serious problems with your Mac you might as well complete the exercise by repairing your hard disk as well. You cannot do this from the same start-up disk. Reboot from your install disk (holding down the C key). Once it opens, select your language, and then go to Disk Utility from the Utilities menu. Select your hard disk as before and click Repair:
Once that is complete reboot again from your usual start-up disk.
More useful reading here:
Resolve startup issues and perform disk maintenance with Disk Utility and fsck
For a full description of how to resolve Disk, Permission and Cache Corruption, you should read this FAQ from the X Lab:
Apple's advice on general maintenance:
My only concern with SSDs is have they yet made it possible to securely erase the drive before giving the machine to another individual? I know there was concern about that in the beginning, as erasing an SSD using the same methods as a hard drive still left behind crumbs that could be recovered a hard drive would not give.