Dell dimension 1100

I'll give an answer that is based on reality, not advice to go buy a faster computer:

Unload the system tray of any programs that you don't actually need on a continuous basis.

I see people all the time running their machine completely on the Windows PageFile because they have so many programs start with Windows that there isn't any memory left for Windows and applications to use anymore. Their machines slow down to the absolute hard drive access speed to swap in/out every segment of every program they use. Ask yourself, Do I really need Apple Quicktime running all the time? Do I really need some cute hot-key poller running all the time? The list gets very large sometimes. These are programs that a person uses once a week, yet they are fully loaded at all times, ready for action but at the expense of system RAM and machine performance.

Right-Click these un-needed programs and see if they offer options, and if one option is to start when Windows starts, uncheck it.
Quiicktime has a sneaky way to stay in the tray, but is dis-abled by unchecking the option to make videos launch faster under the "Browser" option.
If not dis-abled there, it will re-establish itself in the registry to start with Windows.

Get "Detect Autoruns" at

http://technet.microsoft.com/en-us/sysinternals/bb963902.aspx

and turn off un-needed programs under the "Logon" tab.
You can go back and turn them back on if really needed.

Disable installed programs only. Don't go disabling everything, some of these things you do need all the time.