ms outlook 2002

i am running on Windows 2000 professional SP4 with ms outlook 2002 SP3..

On ram 512DDR Ram

The Ms outlook 2002 pst pointed to my network pc (for tape backup purposes)..
which the size is around 600mb..

So whenever i open MS outlook…it starts very very slow and sometimes hangs…why this happen??

Before i convert it to win2k…which previously is Win98se…with ms outlook 2000 (pst also around 600mb)..its so fast..

Why?? is it Win2k pro..bug or wht??

Please help
any solution..