There is no Windows 7 driver available yet for your webcam from Dell but the Vista driver might work. Try downloading the driver from here http://support.dell.com/support/downloads/download.aspx?c=us&cs=19&l=en&s=dhs&releaseid=R198114&SystemID=INSPIRON1545&servicetag=&os=WLH&osl=en&deviceid=19297&devlib=0&typecnt=0&vercnt=1&catid=-1&impid=-1&formatcnt=1&libid=17&typeid=-1&dateid=-1&formatid=-1&fileid=273878

And then install the software. Before running it you can right-click on the icon and run the software in"Vista compatibility mode" under the properties tab. The driver should work on Windows 7. If not you will need to wait for an updated driver from Dell.

Ive looked into it for you and your model is capable of using the Vista drivers for windows 7.
So download the driver here
http://support.dell.com/support/downloads/driverslist.aspx?os=WLH&catid=-1&dateid=-1&impid=-1&osl=EN&typeid=-1&formatid=-1&servicetag=&SystemID=INSPIRON1545&hidos=W732&hidlang=en&TabIndex=
Its under Input Devices.

Hope This Helps! Please Rate!

Here is a link to the Dell site for all Win 7 drivers for your Inspiron 1545

http://support.dell.com/support/downloads/driverslist.aspx?os=W732&catid=-1&dateid=-1&impid=-1&osl=EN&typeid=-1&formatid=-1&servicetag=&SystemID=INSPIRON1545&hidos=WLH&hidlang=en&TabIndex=