Eleanor - you should really start a new thread for your problem. And I'd suggest it might be better in forum779 (XP) that here in hard drive issues (as its not obvious its a hard drive or indeed a hardware issue, and its your operating system that's not working).
Can you clarify some of your post as well please:-
It will start in safe (or different) modes but always returns to the black screen
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What does this mean - or different, does that mean VGA mode and last known good? When you say its starts - how far does it get before you get the black screen?
You say problems started after installing ie7 and defender. Immediately after - or after several hours, days, weeks?
Did you install anything else on your laptop during this period?
The Defender issue may not be pertinent to the display issue - which sounds like something has corrupted the display drivers (if you're getting display before windows starts properly, I'd suspect the actual graphics adapter is working ok. But there may be a general 'corruption' of filestore issue - that's affected defender and display drivers. Do you have up to date anti-virus software installed?
I would have expected the laptop to boot from the recovery DVD - but what actually did happen? (the bios may be set to boot from hard drive before CD/DVD drive - in which case the recovery DVD will not boot till you change the boot sequence. You can do this by entering the bios settings - should be a prompt onscreen for which key to press - I think its usually F2 for Toshiba, but may be another key(s). Alternatively, many laptops also display a key to enter the boot sequence - usually F12 - if this is displayed, try that. If you have a recovery CD, do you also have an XP install CD? If so, you could try recovery console - then run chkdsk c: /p.
Normally VGA mode (from the safe mode menu) will give you a display in windows when the display driver is casuing problems. If its not, suggests the default windows vga driver is corrupted too.