I got annoyed by a low disk space balloon which pops up every x minutes. Off course it's better to increase the free disk space, but when that isn't really an option, you can use the following trick to disable this irritating balloon:
- Start regedit.exe;
- Browse to HKEY_CURRENT_USER\ Software\ Microsoft\ Windows\ CurrentVersion\ Policies\ Explorer
- If the NoLowDiskSpaceChecks object doesn't exist, create it as a DWORD;
- Set NoLowDiskSpaceChecks to a value of 1;
- Log off and then Log back in
Source
Hope this helps,