Hi Delon,

Unfortunately the 3550 - 24 PWR only supports Cisco prestandard PoE. Here are a few reference docs with this note;

Cisco PoE Product Snapshot

http://www.cisco.com/en/US/netsol/ns340/ns394/ns147/ns412/netbr09186a00801f4329.html

Catalyst 3550-24PWR

24 10/100 Cisco prestandard PoE ports and 2 GBIC-based Gigabit Ethernet slots

http://www.cisco.com/en/US/docs/switches/lan/catalyst2950/software/release/12.1_19_ea1c/release/notes/OL543002.html

Cisco Catalyst 3550 24 PWR (Cisco prestandard PoE only)

http://www.cisco.com/en/US/products/ps6021/prod_brochure0900aecd8017bf5f.html

Hope this helps! (I know its a bummer :(

Rob