sluggish network transfers (LAN)

slow speed on LAN.
browsing is ok but trying to get anything copied from one host to another
takes ages.
The network is set up correctly.
It consist of two laptops, wireless acces point with integrated switch.
One laptop is connected via Ethernet cable, other via WLAN.
The average speed isn't more then 1MBytes per sec which is far below what I
expect.
All devices are set to 100Mbit Full Duplex except WLAN obviously which is
set to 54MBit as it is 802.11g.;
CAN ANYONE EXPLAIN TO ME WHY ITS SO SLOW???

Aah, one laptop is XP Home SP2, second is Vista Home Premium, both legal
licences.
Router/switch/gateway is Linksys WAG354G V.2