To connect 2 computer directly without router with wireless  in Windows XP … Just make sure your computer and the other has wireless …

Than you can do it like this ….

In Computer 1 

1.  From Start Menu Click : Start -> Setting -> Network Connection -> Wireless Network Connection

2.  Click Properties -> Wireless Network -> Advanced and Choose Computer to Computer (ad hock) network only and click OK

3.  Then Click Add … And fill your wireless name for example : wireless1 … just remember to choose Data Encryption with disable . then click OK
4. After that  choose General …  And Click Internet Protocol (TC/IP) in ListBox

5. Click Use the Following IP Address . And Fill

IP Address = 192.168.0.101

Subnet Mask = 255.255.255.0

Than Click OK

In Computer 2 :

1.  From Start Menu Click : Start -> Setting -> Network Connection -> Wireless Network Connection

2. Click Properties -> General ->   And Click Internet Protocol (TC/IP) in ListBox

3. Click Use the Following IP Address . And Fill

IP Address = 192.168.0.102

Subnet Mask = 255.255.255.0

Default Gateway = 192.168.0.101

Click OK

4. After this from your Wireless Connection you can do connect 2 computer with wireless without router