We have been discussing about wireless routers in this thread
Good WIFI N series router
I suggested ppl to go for Linksys...rather than Netgear/Belkin/D-Link, they may come at a premium price but worth every rupee.
Now not to disappoint you as you have already made your purchase, please try disabling your firewalls. Moreover, you may try going to "My Computer" icon, right click on it and then click on "Properties". Select the Device Manager button under the Hardware Tab. Select your network card from the list (should located under network adapters) right click and select properties and under the Advanced tab look for Speed & duplex in the box. select it and change the drop down menu from Auto to 10mb/half duplex. This should do the trick.
Lastly, I can suggest you to give this router back to the vendor and ask for a linksys as replacement. Pay the difference and you will never have to worry about speed.