2nd hd install, no screen normal mode

Hi, I've searched on this forum for some answers (and got some, not yet tried any). I installed our wXPproSP2 OS to a second drive (leaving the 1st install intact & working on its own drive). The new install stops near the last step: the monitor is not activated in normal mode, the PC just sits there. The monitor is active in safe mode. I tried reducing the resolution to 800x600 (the minimum given), but still normal mode doesn't give screen.
-I didn't disconnect the original drive while installing XP to the new drive. Did this mess things up? (I've looked at the MS link recommended here on parallel install, it doesn't say to disconnect drive with older system.)
-I haven't touched the BIOS yet. If I adjust it, would this make the monitor act normally? (I think not, since monitor does act normally in safe mode.)
-This PC has 500 MB RAM, 1.8 GHz P4, ATI Radeon VE AGP card, haven't seen any major issues with it in 3+yrs. with 1st install of OS (the drive is full however, and minor OS issues are increasing).
-Should I simply run the XPSP2 install CD again, and let it repair its install?
-I want this PC to dual boot for a while (once the 2nd boot is working well), until all is transferred to larger drive. So I presume that I do keep the 1st drive disconnected, do only boot from the 2nd drive at first, and then connect both drives? Or is it the other way around (once the 2nd install works, I disconnect it, run the PC as before from the older drive, and then connect the 2nd drive, keeping the 1st drive as C ? I also have TWEAKUI, but I'm concerned about MBR problems.

Thank you.

 

When you say the install stops at the last step with a blank screen, do you mean the last step of install?

Or that you finished the install but get a black screen when you try to boot into that XP instance?

http://support.microsoft.com/KB/314503
http://support.microsoft.com/kb/282195

If using an NVIDIA display adapter, and you have finished the installation, use Safe Mode and install a new driver set.