Saving main memory will definitely speed up your PC to some extent. When you run any application on your PC,  xp stores files known as DLLs in memory and even if you close the program, xp will leave it there for later use which slows down your PC. Here’s a registry fix for this problem

a). Go to start and open run, type regedit and enter  to open registry settings.

b).When regedit is opened browse to HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrent Version.

c). Select the explorer folder.

d). Now click Edit->New->DWORD value and name it AlwaysUnloadDll, press enter.

e).Now double click it and assign it a value of 1.

Exit regedit and reboot.