running more than 1 application slows system

[Ortica]

symptoms:
-shutting down is slow
-starting up is slower (the standard window music on startup sounds choppy)
-opening up applications (word, excel, messenger, browser) is VERY slow
-opening up multiple applications is painfully slow
-once an application is open it works fine
-it takes firefox browser approx 60 seconds to load; once loaded; it works fine
-playing videos from dvd or from youtube is very choppy

things ive done so far to fix:
-ran avira antivir free antivirus
-defag, spybot, avg, ad-aware have all been run
-delete programs rarely used
-half my hard drive space is free

system specs:
-compaq presario laptop
-512MB
-80 GB harddrive


im wondering if i have a problem with my RAM or some other hardware??
i do not have my installation CD.

[law99]

I have 512MB, are you using XP? How long have you had the PC, new problem? What is your AV?
Start>RUN>msconfig (typed in)>OK>Startup, How many things are running?

Antivir I see, you are using only one active firewall, AV, Antivirus?

[Ortica]

i am using XP and i disabled all startup prgms using msconfig.
my laptop is a few years old.
ths has been a problem for a month now.