all on line games lag

I just bought a dell inspiron 518 desktop computer for my son with vista.
Every online game toontown, ruinscape, zwinky have significant delays. The
wireless router to our fios network is fine, itunes songs download in
seconds, and internet webmail is fast.

We never had any of these problems on his old, 512ram $300 laptop running
xp. What is wrong vista an on line gaming? Is there something I can adjust
so these games don't lag? The specs are Inspiron 518 Intel® Pentium®
dual-core processor E2180 (1MB L2, 2.00GHz, 800FSB)
Operating System Genuine Windows Vista® Home Premium Service Pack 1
Memory 2GB Dual Channel DDR2 SDRAM at 800MHz (4 DIMM)
Keyboard Dell Entry Keyboard and Dell Optical USB Mouse
Display Dell E198WFP 19-inch Wide Flat Panel
Video Card Integrated Intel Graphics Media Accelerator 3100
Hard Drives 250GB Serial ATA Hard Drive (7200RPM) w/DataBurst Cacheâ„¢
Media Card Reader No Floppy Drive or Media Card Reader
Mouse Mouse included with Keyboard purchase
Modem No Modem Option
Optical Drives 16X DVD+/-RW Drive
Sound Card Integrated 7.1 Channel Audio
Speaker No speaker Option
Wireless Internal PCI 802.11g Wireless Network Card

ANY help is greatly appreciated. T