G400DH32 + PIII 600B

[maccoro]

I have updated my system from PII-400 to PIII 600B (FSB=133), 128MB PC100 SDRAM, AHA2940U2W, MB Gigabyte 6VXE+ with APOLLO PRO 133 VIA chipset. I have latest MB BIOS, G400 BIOS and PD541. While really faster in 3D gaming, it has become incredibly slow in windows movements and in 2D programs like ACLT2000. All is in italian version. I have tried a lot of settings. PCISPY shows AGP 2X.
My mouse is PRIMAX 3 buttons + wheel.
Do You have any idea? Thanks!!