Just finished repairing an Acer 3500 which was freezing on startup and running very slow, mouse and keypad would stop responding. To shut it down I had to remove the power cord and battery. It would start in safe mode without any problems. The following fixed the problem.
Start in Safe Mode. Open Device Manager and expand Batteries.
Disable the entry "Microsoft ACPI-Compliant Control Method Battery".
Close and restart notebook in normal mode.
Hope that corrects the problem it did for me.