Looks like there are not Windows 7 drivers available for the Dell Inspiron 1520 - http://support.dell.com/support/downloads/driverslist.aspx?c=us&l=en&s=gen&ServiceTag=&SystemID=INS_PNT_PM_1520&os=WLH&osl=en&catid=&impid=
You can try giving the Vista drivers a shot.
Cheers,
Cassandra
Microsoft Window Outreach