Let me double up on the “replace the adapter” comment. Go spend a little money on a USB adapter and disable the built-in one. My wife’s HP wireless decided to crap out after less than a year. It’s easier to run down to the store and pick up a USB version of what broke and install it instead of trying to go through the customer support path. Maybe it cost me a few more bucks - but the headache is solved (and wife isn’t nagging about her computer not working ;-)
This allows you to get a clean install on a new driver AND avoid the problem if it’s really a hardware issue. So it’s a two-fer.
IF you still have a problem after going to this extreme - time to replace or re-install Windows 7. Can I interest you in a nice Linux install - perhaps Ubuntu? ;-)
My wife's HP Vista machine has the same problem. The wireless drops the connection and won't reconnect until I reset the router. I bought an "N" router, reset the "sleep" function on her machine and typed in registry patches from MS. Although it drops it less frequently now, it's still a headache. The XP machines I have don't experience this problem. The USB wireless is a good idea. Occham's razor to the rescue!