BleepingComputer.com: computer barely working

Not sure if anything can be done, but my computer is barely functioning - IE takes forever to load, outlook express slow, programs freezing then halting, can't even backup because too slow and freezes. tried combo fix but get an error msg saying ' c.bat is not recognized as an internal or external operable program or batch file' ... i am also using administrator account. i have xp. please help. thanks