Is my Laptop MXM compatible?

I have just purchased a Dell Inspiron 17, which comes with integrated Intel GMA X4500MHD graphics, but according to Wikipedia it can take ATI Mobility Radeon HD 4330 with 256 MB or 512 MB of graphics memory. Now, according to various vendors, these are MXM powered, but not all laptops are, and my Dell is not listed as being MXM powered. So, can anyone tell me, does this mean that I can spend 40 quid on an ATI Mobility Radeon HD 4330 with 512 MB of memory, and expect it to work?