Wi-Fi connectivity lost after sleep mode?

First, since it is not clear from your position as to how you came about running Windows 7 on this laptop (came pre-installed, updated, made a clean install), or if you are running 32-bitor 64 bit Windows 7, then I suggest you go to the support website of windows. It would give you a better insight.

Other than I can only tell you to, connect the service tag number and see what Dell may be available in the way of drivers and utilities updates (chipset, wireless, biographies, etc.), as is generally considered a good idea to ensure that these are all as current as possible.

It also does seem to make any difference at all if the machine is running on battery instead of AC as to whether or not the problem. There is no other place to look and possibly make an adjustment to the way it behaves the wireless adapter, you can perform advancedconfiguration changes within the options to change his plan to "save mode" to "maximumperformance" and considering the bus architecture and adjust the PCI Express link statepower management settings outside. However, changing these parameters can inhibit your ability of laptops to enter sleep mode, so if the change presents more problems thanthey are actually resolved may have to switch back to its original state.