I've never heard of it, do you mean that it doesn't have the ability to reverse the decision (restore) you made (poor design) ?
There should be some form of quarantine/restore to recover from such occurrences, if not you paid too much.
The file you would appear to have removed from the start-up list is ashDisp.exe, the avast system tray icon and on-access interface. None of the other elements should have been effected so you should still be protected. What avast processes have you got in task manager, they begin with ash or asw ?