Drive Health Warning - More Info?

On my C drive I get a yellow Warning message, but have no idea what's wrong. Documentation has no information about drive health. External hard drive has Good health.

Drive is about a year old. What's happening?

Running Windows XP SP 3

Defraggler V2.09.391

Thanks in advance.

Mark

What is the make (brand) and type (SSD or spinning platter) of the C: drive? Most manufacturers have free diagnostic programs on their website that you can download & run to give you more specific information about the drive.