Instructions
Navigate to the Planet Elder Scrolls website and enter "Soul Gem Discharger" into the search bar at the top of the website. Hit "Enter" to continue.
Select the "Soul Gem Discharger" mod from the list that appears. Click the "Soul Gem Discharger.zip" file and then click the "Download Now" prompt that appears in the middle of the website to download the mod.
Save the mod to your desktop by following the downloading pop-up prompts. Extract the usable mod files by right-clicking the "Soul Gem Discharger" folder, selecting 'Extract Files to..." and then selecting the desktop to extract the files.
Open the Soul Gem Discharger folder, press Control+A, then Control+C to highlight all of the files and copy them. Navigate to your Oblivion/Data folder, right-click an open space and select the "Paste" option to activate the mod.
Start a saved game of Oblivion and go to the Imperial City Market District. Go to the Copious Coinpurse and buy the Soul Gem Discharger item from the merchant for 500 gold.
Left-click the Soul Gem Discharger item in your inventory to bring up the "Discharge" menu. Select one of your soul gems, then press "Accept" to get rid of the soul in the soul gem.