Your fighting with a built-in limitation of the eval version of the Keil tools. This "2K offset" is a "feature" of the limited version of the compiler that keeps it from being useful to make shippable code for a small memory (aka 2K FLASH) microcontroller.

When using C51 you need the STARTUP.A51 code (or a derivative of it) to get the microcontroller initialized for the C code execution environment. So you may also be stuck there.

As far as moving around the base address of the program Keil has an application note on the subject of relocating the interrupt vector table. This ends up also relocating the user code to another location as well. Check for this at the www.keil.com web site. This feature prolly does not work with the eval tools.

Finally it sounds like you may be ready for something beyond the eval version of the Keil tool set.

Michael Karas