have discussed this before on this forum...

pim.vol is a big memory eater. that stores your contacts and such. if you have a lot of contacts then thats one reason.

if you have your web browsers cache stored in main memory they eats up memory too.. along with the history, temp folders, sms messages, stored/deleted messages,sent messages...
check on those things and clean it out... you may also have some program storing some log file in your main memory....

pocket mechanic will move many things form main to storage memory and set the appropriate reg entries so that all works as it should. i have been using that program for years...