Ram is the fast acting memory for things you are currently doing then it saves info onto your main hardrive. If you look down at the bottom right you will see little icons next to the clock.
If there are lots of icons then this means lots of programs are running hidden. You should close things you are not using - most of them you can set to not run in system tray or hidden. They are using Ram so closing them if they are not needed will free up space.
If you want to add ram it would require opening up the pc case and adding if space permits. Depending on the age of your pc you may find it hard to find compatable hardware.
Its worth once a year backing up data and blowing the pc away and starting fresh.
Spyware also slows your computer down so if you havent got programs such as spybot and adware they are worth getting and running once a week.
The Icons I have (some which are hidden) are as follows:-
AVG running scans
Nokia PC Suite
Zone Alarm
Phone Selector (not connected)
AVG Anti-Virus Free (this one is hidden)
Dell Support
MediaFace 4.0 Intergration
Corel Photo Downloader (this one is hidden)
Local Area Connection
Volume
Safely Remove Hardwear (this one is hidden)
If I close any of them down, how do I get them back when I need Them?