Check the wireless connection in Safe mode with networking (restart the computer and tapping F8 on Dell logo Select Safemode with networking).Check if the wireless connections is still slow in Safe mode with networking in IE9, try updating the update the wireless router's firmware to the latest available.
Also, I recommend, reset IE9.
Please follow below mentioned steps to reset IE:
Close all Internet Explorer and Windows Explorer windows that are currently open.
Your changes will take effect the next time you open Internet Explorer.
For more information, I have provided a link below which can fix the issue:
Below mentioned link would also help you with the settings for wireless internet in future:
Kindly revert and let me know for further clarifications.