Re: Windows Vista Recovery D:
Chances are, the system monitoring is just going nuts on you now because your primary disk space is also filling up. If you can't see anything in that second partition/drive, it's nothing to be too alarmed about. Most users never notice the low disk space alert, and in 99% of the cases, it's perfectly normal for Windows to ignore it and then suddenly start popping up disk space warning messages when the free space hasn't changed at all.
if you're paranoid, run a full virus scan and then run your system through full sweeps with Malware Bytes and SUPERAntispyware. If all of those come back fine, then I wouldn't worry about it.