It will zap stuff like the name of the last catalogue and whether you've chosen the "open last catalogue" or "let me choose" option, whether you've set top and bottom and left and right panels to auto or manual, whether panels are expanded. It would indeed be safer to copy it to your desktop, though IMO it contains nothing of huge value. I should have said double click on the catalogue to restart LR.
Another thing to check is whether it's the catalogue or Lightroom which is broken - my bet would be the catalogue. So rename it in Explorer, then restart LR and see if it starts. This will create a vanilla catalogue in My Pictures - you may be able to use File > Import from Catalog to recover your work (effectively sucking in the old file and hopefully bypassing the problem). There is someone at Adobe who has been helping out with crashed catalogues, but let's cross that bridge later.
John