The log file for database 'tempdb' is full. Back up the transaction log for the database to free up some log space sql 2005 sp3

tempdb

Database_size 891.44

Unallocated space 871.27 MB

reserved   data          index_size      unused

552kb         160kb     304kb              88kb

My hard disk size 32 GB free and it is in SIMPLE mode.

when i am executing the script it showing "The log file for database 'tempdb' is full. Back up the transaction log for the database to free up some log space"

I am using  SQL 2005 sp3 and XP machine. Can any one help me how to solve this problem ?? urgent please.