Leave the Identity field out of the Excel file... it's not needed.
In the DTS Import/Export wizard:
1. define your spreadsheet as source
2. define your SQL database as destination.
3. select "copy tables and views..."
4. select your source sheet (eg. tblExcel$)
5. within transformations dialog, choose "Create destination table" and click on "Edit SQL"
6. In the CREATE TABLE statement insert the first column as "[IDField] int NOT NULL, " then OK.
7. DON'T select "Enable Identity Insert"
That should work for a new SQL table.
Cheers,
- Mark