I have created two VLAN in my switch network. One of computer whis OS is XP-prof. having two landcard. I have asigned two different IP addresss for different VLAN. Now I want to access both the network at the same time. Is it possible?

Yes. You can also do this with only one NIC. You can assign two IP addresses to one NIC, one on each network. The port that you plug your computer into must be a Trunk port. Trunk ports are members of all VLAN's.

If you use two NIC's, the ports must be set to the approprate VLAN for your NIC to see the rest of the devices on that VLAN.

Only one gateway address can be assigned on your computer. So if you want to perform routing on both of your networks, you will need to use a separate router (or your switch if it is Layer 3) and add routes for each of your VLAN's.