Microsoft Windows XP will generate an alert when disk space gets low on a partition. When you click on the message, Disk Cleanup Wizard starts. When XP free disk space reaches 200MB, the following alert displays for 10 seconds, once per session:

You are running out of disk space on [drive]. To free space on this drive by deleting old or unnecessary files, click here.

When XP free disk space reaches 80MB, the following alert displays for 30 seconds, every four hours, twice per session:

You are running very low on disk space on [drive]. To free space on this drive by deleting old or unnecessary files, click here.

When XP free disk reaches 50MB, you receive the following message for 30 seconds, every five minutes, until free space is above 50 MB:

You are running very low on disk space on [drive]. To free space on this drive by deleting old or unnecessary files, click here.

You can disable these alerts using the following Windows XP registry hack:

Hive: HKEY_CURRENT_USER
Key: Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
Name: NoLowDiskSpaceChecks
Type: REG_DWORD
Value: 1 disables alerts