[MOSS2007] the size of C:\Documents and Settings\[Service Account]\Local Settings\Temp folder growth

on MOSS2007 Server C:\Documents and Settings\[Service Account]\Local Settings\Temp is biger and biger (8GB now). Different documents from SharePoint (.doc, .pdf, .jpg, . xlsx .....) are saved there. I see also one WebTempDir folder, it is but empty. What is it? Why so many sharepoint documents are saved here ? Are they cache? I have deleted all the files here one time. They dispear but again after a few minutes. how can I do to stop it? It takes too many storage.