Note:

For users without write access to the C:\Windows directory:

A file called ncbi.ini is required for the currently-implemented blast 
utilities in BioEdit.

When blast or database formatting functions are used by BioEdit, 
this file is first read, then written to be compatible with BioEdit,
then re-written to its original state after the BLAST function runs
(for compatibility with any other program(s) that use ncbi.ini).
This causes a problem for users without write access to C:\Windows.

To turn off the feature, go to Options->Preferences\General and uncheck
the checkbox labeled "Do not write to ncbi.ini (manually create ncbi.ini)".

You may need to manually create the ncbi file (one time only). To do this, 
create a plain text file called C:\Windows\ncbi.ini with the following 
contents (next four lines), substituting the folder in which you have 
BioEdit installed for "<BioEdit install folder>":


[NCBI]
ROOT=C:\
ASNLOAD=<BioEdit install folder>\tables\
DATA=<BioEdit install folder>\tables\


for example, for a default installation, the file would contain (four lines):

[NCBI]
ROOT=C:\
ASNLOAD=C:\BioEdit\tables\
DATA=C:\BioEdit\tables\


Save this file as C:\Windows\ncbi.ini.
Keep "Do not write to ncbi.ini (manually create ncbi.ini)" unchecked, and 
the BLAST functions should work without requiring write access to C:\Windows.