If I choose to wipe the entire drive, will ccleaner delete all applications? Will it delete the OS?
Yes, if you have installed your OS+apps to the drive you're going to wipe (usually C:\ is your home/systemdrive).
It wipes/deletes everything, so be careful with the tool.
Edit: Though I haven't tested it, but I guess you can't wipe your systemdrive (completely) while it's in use and especially if CCleaner is installed to the same drive.
"Entire Drive will erase all of the files on the drive. WARNING, this means the whole of the partition will be erased. The drive will still be formatted, but all data will be erased. For safety reasons, this feature is disabled for the boot drive." from http://www.piriform....free-disk-space.
Check also http://forum.pirifor...howtopic=33599
To clarify nodles' response:
Use it on a non-system partition and it will delete ALL of the data.
Use it on your system partition, and it will wipe free space.
I have to admit that my post wasn't very clear, sorry for that.
Thanks for clarifying, Winapp2.ini.