they should have loaded automatically, have they ever worked before win 7.?
try a few things.
1.) do you have the Dell drivers CD that came with the unit, if so load drivers from there.
if you get a prompt about compatibility then just force feed them, they should work regardless
32-bit is the more compatible with older drivers than 64-bit.
2.) go to device manager and look for the unknown hardware or hardware with the exclamation or question marks.
right click on them and select update driver, make sure you have an active internet connection.
3.) go to Dell dot com and download specific drivers if you do not already have them.http://support.dell.com/support/downloads/driverslist.aspx?c=us&l=en&s=gen&os=WW1&osl=en&catid=&impid=&SystemID=PLX_GX620