Criteria for low disk space warning on XP?

Question

According to this article, it says the low disk space warning appears when there is less than 200MB of disk space. However, I find this not to be the case. Two test examples:

1) I create a 3GB FAT32 TrueCrypt archive as a file container and mount as a drive letter. If the disc volume has 158MB free space (less than 200MB as stated in article), I do not see the warning. I only see the warning if I have something like less than 100MB free disk space (I am unable to verify the exact amount for sure).

2) I create a 300MB FAT32 TrueCrypt archive as a file container and mount as a drive letter. If the disc volume has only 18MB free space (less than 200MB as stated in article), I do not see the warning.

In both cases these were mounted as local drives on XP Home SP 3. Using TrueCrypt 7.0a.

I have not made any registry changes to disable the low disk space feature, or changed how it works.

Can anyone clarify the low disk space behaviour and the criteria?

Answer 1

I had some thoughts that have been very hard to prove as I searched and searched, but I suspect that those drives are of a type that Windows does not poll for low disk space.

This is for Windows 7, but surely many of the same rules apply for XP, so I quote:

Windows 7 does not poll Zip Drives, Floppies or any other “removable” media drives.

http://support.Microsoft.com/kb/2547929

My first thought is that it is treating them as one of those types of drives, in particular, as a removable media type drive.

As a note, I confirmed that it will indeed report low space regardless of whether it is NTFS or FAT32, so that is not an issue.

Answer 2

From the testing I have done:

The low disk warning is normally shown after the drive is mounted and there is less than around 100MB free (not 200MB as the article suggests).

However, there are two exceptions:

1) For small drives (say 300MB in total), the low disk warning does not seem to show at all.

2) Is a drive is mounted as external rather than local (via an option in TrueCrypt), the low disk warning does not show at all.