Very slow also to increas memory

You need more memory. If you have windows xp you need at least 512 memory.

It depends what you use your computer for,

Surfing
Gaming
Ect Ect Ect,

i have a dell optiplex gx 260 with 256mb ram for surfing, ok in speed ect ect

you may have a virus on your computer, that was a problem with my brothers computer, it ran very slow, i upgraded the ram to 1.5g from 256 and wernt mutch diffrence,

The point im trying to make is that it may not be ram that you need as xp runs on a 64mb ram (I TRIED IT)

It may be spyware, adware or a trojan,

Try this program "spyware doctor" It will scan your computer for viruses adware spyware ect.

The link to spyware doctor is:
http://www.pctools.com/spyware-doctor/?ref=afl_nenextech&gclid=CNLm3ZSgjZwCFZ4A4wodRxzNYg

(Copy and paste into your browser)

Then put the scan results on here