There are many atheros mini pci cards which will fit your machine. The latest available chipset is AR5006 which you can read about here:http://www.atheros.com/pt/AR5006Bulletins.htm
(the AR5008 is currently on the website but no products are available to buy that I am aware of and AR5007 is the access point chip in case you are wondering why the numbers skipped one).
The top of the range chip is the AR5006XS which supports a/b/g and superG (108mb) The super G will only work if you couple it with a superG router.
This card on ebay uses the AR5006XS chipset:http://cgi.ebay.co.uk/Atheros-AR5006...QQcmdZViewItem
I have an Inspiron 9400 which is pci express (different shape card to yours) and I am using the pci-e version of this chipset (A Gigabyte card using the AR5006EGS b/g only chip) coupled with a D-Link DSL-G624M router and it is a wonderful combination. I have superG working at 108mb (two notebooks) and the performance is flawless. no more dropping out, connecting and re-connecting I had with the Intel. The Atheros card is also so sensitive that I can see two routers in my area that were not there with the Intel.
Hope all this helps.