|'last known good configuration' would be best. 'Safe mode with networking' would also make available system restore so you could choose a date to restore prior to any changes you may have made (or errors). If you cannot get to any of these, you will need to do a 'repair install'. This can be done from a windows install disk, a recovery disk, or a recovery partition (accessed usually through pressing a specific 'F' key while booting) though I am not sure if the last one will allow a repair of only a return to 'original configuration' (no files or programs or updates). If you can perform a windows repair, you should be all set, if not, then you may need to recover your files first before doing a 'restore' to your drive. Google 'live linux', find one you are comfortable with, download 'ISO image' and burn to CD. The Live linux will run off the CD and your RAM without installing and allow you to copy your files to another drive like an external hard drive. Then you can reinstall or 'recover' to factory installation if needed.|
You have to be a little bit crazy to keep you from going insane.