Windows Disk Cleanup is a built-in tool to help reclaim disk space. Under certain circumstances, however, it can nag the user and become an irritation. This may happen when disk space is critically low, in which case the notification can be disabled. Alternatively, the system may be running the application automatically at scheduled intervals. In this case, the task can be deleted.
Disable the Low Disk Space warning (XP/Vista/Windows 7)
Start the Registry Editor by clicking "Start," selecting "Run," typing "regedit" and pressing "Enter" if you are using Windows XP. If you are using Windows Vista or Windows 7, click "Start" and type "regedit" into the Search field. Press "Enter."
Find and select "HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer."
Create a new entry in this location. Click "Edit," select "New" and choose "DWORD Value." Type or copy and paste "NoLowDiskSpaceChecks" into the box and hit the "Enter" key. If this already exists, move to the next step.
Make the new entry positive. Select it, click "Edit" and choose "Modify" or simply double-click it. Enter "1" and click "OK."
Quit the Registry Editor and restart your computer.
Delete Scheduled Task (XP)
Open Scheduled Tasks by clicking "Start," selecting "All Programs," choosing "Accessories," clicking "System Tools" and selecting "Scheduled Tasks."
Find and select any entries in the list that refer to Disk Cleanup. Hold the "Ctrl" key while clicking to select multiple items.
Click "Delete Item" and select "Delete the selected items" in the sidebar to the left.
Disable Scheduled Task (Vista/Windows 7)
Click "Start" and type "Task Scheduler." Hit "Enter."
Find any entries in the Active Tasks box at the bottom that refer to "Disk Cleanup" and double-click them.
Click "Disable" in the sidebar on the right and close Task Scheduler.
Disk Cleanup warnings may be annoying, but they're there for good reason. If your hard drive is too full, your computer’s performance will suffer badly. The best way to get rid of the alert is to free up disk space. In addition to running Disk Cleanup, you can delete old downloads, finished games or watched movies, or move them to external hard drives or optical discs. Try to keep your hard disk, especially your system drive no more than 85 percent full.
Damage to the registry can be disastrous. Always back up your registry before editing it.