But you can start the task manager before the virus loads, when the virus loads there are only a few that close task manager while it is running, viruses mainly prevent new windows from being opened rather that terminating existing ones, once the process is ended i usually do a start>run, MSCONFIG, and locate the startup process, the virus will be located in there so you should find its exact name or the directory it resides in, this way you can do a scan of the registry for that specific directory and remove it (or virus), also do a local search and remove the folders/shortcuts etc. Some viruses also have an auto install on startup which can also be found in the C:\program files\common files\uninstall.