I'm guessing that you can't use more than 4 characters. Obviously the entire Dell Service Tag is unique, and this would be the best way to go. MAC address is apt to change when parts get replaced or when a different network device is in use.
Using a small sample from one of my environments (700 Dell nodes), I found 4 duplicates in the first four characters as well.
If you had a report from Altiris listing MAC addresses, and wanted to compare it in Excel, and all of your MAC addresses were in Column A, I would do it thus:
- Assuming you have headers, row 1 is occupied by headers
- Starting in cell B2, type the formula =RIGHT(A1,4)
- Fill this cell down to the end of column B
- Column B is now populated with the last 4 characters of the MAC address
- Sort Column B alphabetically (Z to A)
- Starting in cell C3, type the formula =IF(B2=B3,"Error: duplicate","")
- Fill this cell down to the end of Column C
- Column C is now populated with the message "Error: duplicate found" if a duplicate is found if the last 4 of any particular MAC address is found elsewhere on the list
Alternatively, after filling Column B but before sorting, highlight the column and choose 'Remove duplicates,' which will tell you how many duplicates were found. I prefer this method since it lets me identify where the duplication exists.
Does this help?