Hi,
Normally, you tap the F8 Key, not press and hold it, to access list of Startup options, including Safe Mode.
Also, see if you have a F-Lock Key on your Keyboard, which may be stopping you using the F Keys.
And here is another way to access Safe Mode:
"How To Enter Safe Mode Using the System Configuration Utility"
http://pcsupport.about.com/od/tipstricks/ht/smsysconfig.htm
Cheers.