Computer won't boot up

Help, I have a Toshiba Satellite laptop running Windows XP. While on line I was asked to update my AVG program and I said yes. It did the update than said it would restart my computer in order to finish the process. Once it shut down and started to reboot, it stops and give me "A disk read error, press ctrl+alt+del to restart".
I have done this numerous times and still it gives me the error message. I have tried to start in "safe mode" (F8) but it flashes by and won't display and gives me the same message. I can however get into setup (F2). I have put in the Toshiba recovery disk but only give me MSDOS. I sure don't want to lose my hard drive info and I don't want to re format. Any ideas??
Bob 27

From the DOS prompt you type in "chkdsk" (without the quotes) and hit enter. This will scan your hard drive for errors.

It may be good idea to test your hard drive.
Unfortunately, Toshiba doesn't provide free diagnostic tool, but you may try Hitachi freeware, Drive Fitness Test: http://www.hgst.com/hdd/support/download.htm#DFT

Somehow yesterday it fixed itself and acted normally. I thought I had disabled the AVG program to keep it from scanning every time I booted up. 
Today as I was in the midst of a program it rebooted and now gives me the same error. But this time I am not in the MSDOS just the "A disk read error occured, Press Ctrl=Alt=Del to restart"
any suggestions? I am able to correspond using my desktop computer.

Soviet Genius, and myself, gave you some advice...

Broni & Soviet Genius;
Thanks for your help. I selected f2, changed the boot up routine  to CD rom first, put in the toshiba recovery disk and it wanted to reformat. I said no and I am currently in ms dos A:\ directory and when I put the chkdsk command it would not recognize it. I think the A directory is simply the recovery disk. I am in a quandary and I don't know what else to do.

"A" is usually floppy drive.
I'd advice you to run Hitachi diagnostic tool. Your hard drive may be bad.