Hi Chris,
First, change the Format of the cells to TEXT. Then enter all the data with prefixed zeros. Next, Save the File with the "save as type": Text(Tab Delimited Text) in the dropwon available in File - Save As option.
When you open the file in Notepad it will have all the prefixed zeros.
PS: When you want to open the File in Excel then you just need to change the extension of the file to ".xls".