File size increases with each save

[Garbunkel]

Hello,

I am working with an Excel file (using Excel 2000, version
9.0.3821 SR-1) that contains four worksheets. One of the
worksheets contains a simple macro timestamp macro &
conditional formatting in one of the columns (to change the
text to a certain color depending on the value contained in
an adjacent cell). The rest of the workbooks contain regular
text data (20000 rows & 8 columns in all), with no macros
or conditional formatting. The regular data was pasted
from several tables in Microsoft Word.

What I have noticed is that the filesize (which started at
approximately 8 MB) increases by a few KB every time I do a
save, even if no data was added, removed or modified. Over
time, this inflated to about 45 MB! I copied all of the data to
a new 4-worksheet Excel file, keyed in the macro &
conditional formatting and saved it. The result was an 8 MB
Excel file that was identical in every other way.

Does anyone know what could be causing the file size to
balloon like this?

Thanks in advance for any helpful input.