Housecall creates a file "tsc.ptn"(pattern file) in your windows folder, I'm assuming this file is similar to Norton's "definition" file, or perhaps this file is also being used to install other files needed to scan your computer.
Try changing the filename to "_tsc.ptn" and go back to
http://housecall.antivirus.com and it'll give you an error "Error#101: Read generic pattern failed!" when you scan.
Common sense tells me this "tsc.ptn" file is safe and housecall just messed up on this one.
Edit:
To uninstall housecall:
http://kb.trendmicro.com/solutions/solutionDetail.asp?solutionId=4577
