My WinXP Pro loads really slowwwww ...... took about 3 minutes from the time i turn on my computer till i get the login screen.

My computer is a 733mhz with 256RAM. Will additional RAM helps? or what could be wrong ?

No you are not wrong. Microsoft recommended 128MB of XP. I assume 512MB would be sufficient to smoothen the OS.

My 512MB ram makes it load nice & quick.