My computer is running so very slow. I have removed temporary files and . Defraging didn't help. Help please

Run a spyware scan, Lavasoft has a free one, and then an antivirus scan to see if it may be a virus or spyware.

Go to Start-->> Run-->> type in 'msconfig'
Go to the 'Startup' tab and uncheck the IM's, Printer software, and other stuff like dell update. Don't mess with the other tabs.
Leave any antivirus, firewall, audio, graphic display. It should help speed up your startup and ease services running.

You can also do Ctrl + Alt +Del and select task manager. Under the performance tab are either the CPU usage or PF usage bars up? You may need more RAM.

How old is the computer?
What CPU do you have?
How much memory?
How big is the hard drive?

As computers age the registry gets full, this requires more more memory to hold the registry which means less memory for other programs.

Spyware/Virus scans are a great place to start but also take a look at a program called CCleaner.
This will get rid of the extra stuff in the registry that gets left over when you uninstall applications.

In addition to Lavasoft AdAware recommended above, another free adware/spyware detector that you should run regularly is Spybot S&D. In my experience, they tend to find different things. The antivirus and CCleaner recommendations are great ones, too.