You need a wireless router.  This assumes that your current dsl modem can connect by ethernet and that the computer currently connected to the modem has an ethernet network adapter.  If the modem can only connect by USB or if you don't have an ethernet adapter in that computer, post back for other, more complicated, suggestions.

Steve

also, i dont know what good routers are out there because they're a lot of them....i need some advice which router i should take that has a firewall and below a $100 price mark..Thanx in advance

i have both usb and ethernet, but i used USB instead.

Unless you transfer lots of large files between computers very very frequently, you really don't need a high speed wireless router.  802.11 b/g routers should be just fine.  It would be able to transfer files between computers at 54 Mpbs.   The dsl connection runs at no more than 5 Mbps, so anything faster than 54 Mbps is overkill.  You should be able to find one on of these for less than $50.  Look at models from Linksys, D-Link, Netgear, and Belkin.

Steve

what's ur dlink router???...can i see specs..maybe it can be a candidate for my search

i'm using a di-524 that I bought for $15 after rebate.  it's not that great.

what do you mean by not that great??

I mean it's a standard cheap router.  It doesn't have the fastest CPU on the market and may not have the throughput of some other models.  It will likely work fine, but may not perform as well as some of the nicer routers, especially with things like WPA turned on.  Whether you'll notice or not depends in part on how fast your internet connection is and what you plan to do with your home network.  For 15 to 20, it's probably a good deal.