For some reason, along the line, my Hard-Drive is Partitioned.....C: and D:.....ALL my "system" stuff is on the C: partition....but, I have HALF of a hard-drive ("D:") that is virtually...well, not virtually is really empty, and un usable...what did I do???
This one is pretty simply solved: grab yourself a partition managing tool (this one is freeware: www.partition-tool.com...), and merge the two parittions.
Then you'll only have one drive (your C drive) but all the space on that, rather than divided up.
as for antivirus...?
Grab AVG or Avast!. Free and easy.