I'd like to suggest the adding of the following to CCleaner:
Removal of MSN connection logs
These are turned on by default by MSN and even if you turn it off via the option, it seems that the option is just re-enabled (From what I've seen, anyway). The logs are located in: "C:\Documents and Settings\%User%\Local Settings\Application Data\Microsoft\Messenger"
My current folder size is just on around 20MB and it was manually cleaned a week ago. There seems to be an option in the MSN option that cleans these, but it didn't work for me.
Side Affects: I did notice after deleting the logs that MSN took a little longer to sign in - and it did take a few seconds longer than usual to fetch the contact list - but I do not think that warrants leaving hundreds of megabytes of unused logs sitting dormant.
Removal of contact list back ups of back ups
Yup, that's right. I'm sure its' common knowledge by now that your contacts are stored on your computer by MSN Live. I do not know why, however, that Microsoft decided it'd be a great idea to create backups of already made backups of your contact list. They are located in "C:\Documents and Settings\%User%\Local Settings\Application Data\Microsoft\Windows Live Contacts". At the present moment in time, I have 4 'Stringed' folders that contain the backups, and two of my own email. I think that having TWO backups on different dates is stupid, and that the oldest one be removed. The logs in this folder are also HUGE, but I don't know what they are for.
Side Affects: Removing the oldest back ups seemed to bare nothing in the way of adverse affects. The logs, I did not remove because I do not know what they do.
If this idea is stupid, please just disregard my post.