When I switch on my computer the first thing I am told is that I have
no NVRAM. Should I have some and if so, how much should I have?

The next thing that happens is that I see all my drives listed. This
stays on the screen for at least 3 minutes.

The boot up then takes place quite slowly and eventually my desktop
comes up with a dialog box which states "The procedure entry point
RtlUnhandledExceptionFilter could not be located in the dynamic link
library ntldll.dll"

This message often appears when I attempt to start various
applications (but not all applications).

My machine appears to be running very slowly when it is working

I am running Win 2k Pro SP4 on a machine with an AMD Athlon 64
processor 3000+. I have 1Gb memory and two Hard Drives. The first hard
drive has 2 partitions, Drive C & Drive E. The second hard drive is
Drive D. The OS is on Drive E.

I hope I have given enough info here to enable someone to advise me.