Should I add more RAM due to slowness of system?

My window XP Pro sp2 boots process takes long period although all the icons for networking, audio, logitech mouse, trend micro antivirus already appeared on the task bar.

My system has 1GB DDR RAM dual channel 400MHZ 184 Pin OCZ brand.
Maxtor HD 200GB
Maxtor HD 120GB win 2003 on second HD
western digital 80GB strictly storage.

I already defraged HD using diskkeeper 10 and optimize PC with tune up utilities 2006.

Should I add more 1GB more RAM ? The system performance seem to degrade after long use. I notice the PC use more paging file although the system isn't runnning any other applications other than firefox browser for surfing the net to get email.