CAD display on screen but too dim for use

Situation: CAD display on screen but too dim for use - RE: VBE VESA mode 107h, 256 colors, only.

Environment:
1. Graphics card: MSI R5450-MD1GD3H/LP (Radeon HD 5450)
2. ASUS M5A97 mobo with AMD FX-6100 (six core) CPU, 2GB DRAM
3. OS: Win XP Pro SP3
4. Display monitor, 23" LCD working normally otherwise
5. App: Generic CADD 6.1 (definitely worth the effort) and it is presently working on two other PCs with different hardware.

PC works normally in all other respects except app's VESA mode. It passes VBETEST.EXE so the mode does work. However, it fails VIDEOTST.bat in VESA mode. The VESA driver, VESA256.VGD, is used in VIDEOTST and is native to the app, and therefore may be suspect. The image on the screen is too dim to tell color rendition, but it appears correct otherwise. Does the same in all other relevant VESA modes. I know nothing about VESA256.VGD. I have been using the app successfully since 1992 with several PCs with DOS, Win 3.x, Win 9.x and Win XP.

I know that this is an archaic application for most of you, is relevant to gamers, but I hope someone out there can be of assistance.

Thanks,
Ckuke