Why does my desktop display go blank after the boot-up screen?

[Ninjapoopy]

Last night I took my pc tower to my friends house to game out, I only brought my tower as he already has extra cables and an extra monitor. Brought it there, hooked it up to his equipment and everything worked fine. This morning I brought my tower back home, hooked it back up to all of my stuff again and booted'er up. Everything seemed fine, I saw the boot-up screen and the loading screen and then right when it is supposed to go to the log-in/enter password screen it goes blank. I still hear the sound that windows makes at that screen, and if I blindly enter in my password I can hear it log in and everything. I tried various power cycles and unplug/plug-in techniques but I always get the same thing. Since I can see the display during boot-up I tried entering safe mode, when I do that it doesn't go blank and everything works fine. It's only when I start it up in normal mode that it will go blank at the log-in screen. I'm using a coby tv/monitor hooked up via VGA cables and I've never had any problems, my desktop doesn't have an hdmi output or I would try that. Haven't had any problems until I simply hooked it up to my friends monitor and then back up to mine. In safe mode I try to mess with the resolution in the control panel but no matter what I change it to nothing happens and upon reboot it defaults back. Please help! I think I just may need to get my graphics card to recognize it again but for some reason it won't. and in safe mode I can't see or configure my nvidia video card driver. Just the system drivers and such. Here is my dxdiag info, since I 'm in safe mode it's not showing the display devices info but I'm using a NVIDIA GeForce 8800 GT. Thanks!
System Information
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Time of this report: 4/26/2013, 02:56:28
Machine name: NINJA-PC
Operating System: Windows Vista™ Home Premium (6.0, Build 6002) Service Pack 2 (6002.vistasp2_gdr.130308-1436)
Language: English (Regional Setting: English)
System Manufacturer: Dell Inc.
System Model: Dell XPS420
BIOS: Phoenix ROM BIOS PLUS Version 1.10 A03
Processor: Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz (4 CPUs), ~2.4GHz
Memory: 3326MB RAM
Page File: 442MB used, 6398MB available
Windows Dir: C:\Windows
DirectX Version: DirectX 11
DX Setup Parameters: Not found
DxDiag Version: 7.00.6002.18107 32bit Unicode

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DxDiag Notes
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Display Tab 1: No problems found.
Sound Tab 1: This computer cannot play audio because the Windows Audio service is not enabled. Use the Sounds and Devices Properties control panel to enable audio.
Sound Tab 2: This computer cannot play audio because the Windows Audio service is not enabled. Use the Sounds and Devices Properties control panel to enable audio.
Input Tab: No problems found.

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DirectX Debug Levels
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Direct3D: 0/4 (retail)
DirectDraw: 0/4 (retail)
DirectInput: 0/5 (retail)
DirectMusic: 0/5 (retail)
DirectPlay: 0/9 (retail)
DirectSound: 0/5 (retail)
DirectShow: 0/6 (retail)

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Display Devices
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Card name:
Manufacturer:
Chip type:
DAC type:
Device Key: Enum\
Display Memory: n/a
Dedicated Memory: n/a
Shared Memory: n/a
Current Mode: 800 x 600 (32 bit) (1Hz)
Monitor:
Driver Name:
Driver Version: ()
DDI Version: unknown
BGRA Supported: No
Driver Attributes: Final Retail
Driver Date/Size: , 0 bytes
WHQL Logo'd: n/a
WHQL Date Stamp: n/a
Device Identifier: {D7B70EE0-4340-11CF-E025-7137AFC2CB35}
Vendor ID: 0x0000
Device ID: 0x0000
SubSys ID: 0x00000000
Revision ID: 0x0000
Revision ID: 0x0000
Video Accel:
Deinterlace Caps: n/a
DDraw Status: Not Available
D3D Status: Not Available
AGP Status: Not Available