two types of express card slot...
express card 54 and express card 34
Your laptop obviously has an express card 54 slot (the wider one) the card you have bought is express card 34 (narrower)
The good news is that express card 34 will fit and work in express card 54 slots just fine.
Have a look at this pic, the top two cards are express cards (ignore the bottom one) you should be able to see why and how a 34 card will work in a 54 slot.
http://en.wikipedia.org/wiki/File:PCCard-Expre ssCard_ZP.svg