BleepingComputer.com: Computer is now running alot slower

Im trying to speed up my aunts 2004 dell insperion 2400 computer that just seems to be getting gradually slower. It has an

intel 4 provessor t 2.530Ghz
256mb DDR SDRAM at 333MHz
integrated intel 3D APG graphics
80BG 7200Rpm ultra ATA Harddrive
Microsoft windows Xp home edition
56K PCI data fax modem for windows(not sure if still using)
integrated 10/100 ethernet
48X Mac Cd-rw drive

Im thinking about adding more ram into it, but im not sure of the proper amount to add, or even know if that will help the problem. The computer starts up at the normal pace it used to, just when it comes up to loading the acctual desktop where the icons are it takes up to 9mins!!!! before you can even use the cursor again, then another 5 mins to open a program.

Please get back to me with any information you have.
thx John

Architecture
DDR SDRAM

Memory connectors
two

Memory capacities
128-, 256-, or 512-MB

Minimum memory
128 MB shared DDR SDRAM

NOTE: Between 32 and 64 MB of system memory may be allocated to support graphics, depending on system memory size and other factors.

Maximum memory
2 GB

Memory type
PC2100 (266-MHz) or PC2700 (333-MHz) DDR SDRAM (non-ECC)