When i connect two computers, i receive message "limited or no connectivity".my o/s is win

When i connect two computers with LAN, then i receive a message that "Limited or no connectivity". I am using windows XP sp2. What is the problem?

When i connect two computers, i receive message "limited or no connectivity".my o/s is windows XP sp2viruses

In addition to the physical connection (crossover cable or hub as in previous answers) you will also need to supply the TCP/IP protocol with TCP/IP addresses manually, unless you are connected to a DHCP server.

Most inexpensive home routers will perform this function if connected to the network and if the PC's have "automatic" selected in the TCP/IP options.

If not using DHCP, you need to manually assign a "local" network address on the same subnet to each computer. Simplest to use a network address like: 192.168.1.xxx where xxx is unique to each computer on your local network, and varies from 0-255 (best to avoid 0,1,254 and 255 since these sometimes have special meanings!)

Another source of this error might be manually assigning the same address to more than one connected PC.

When i connect two computers, i receive message "limited or no connectivity".my o/s is windows XP sp2antispam

Make sure they are in the same workgroup. Windows XP has a tutorial on networking. Select Start then "Help and Support". On the left side, select Networking and the Web". Then select "Networking". This will help you setup your network properly.
It probably means that you're not using a router, and from your description it sounds like you may have just connected the computers directly to each other with a cable. If you do this, they won't be able to talk with each other. Try the same using a hub or a router.
Make sure both computers are on the same operating system with the same updates installed, secondly make sure both computers can connect to the internet by themselves. Last make sure you have no firewalls other than the windows firewall turned on because many of them come default with port forwarding disabled and your router won't be able to reassign IPs to the computers, making the operating system think there is "limited connectivity" because it can't locate the 2nd computer at the address it's looking for it at.
I'm assumming you're trying to connect one computer to another using 1 cable. The least expensive way to do this is to use a crossover cable. You could also buy a switch and use 2 standard ethernet cables.