Came across this useful KB the other day: 906344, The blocked column in the sysprocesses table is populated for latch waits after you install SQL Server 2000 SP4. The technical detail may be a bit confusing. Essentially the SPID is doing a convoluted "WaitForSingleObject"-type block, waiting for a data page to be fetched into memory from disk. If you see a lot of this type of blocking you may want to check your other performance counters as you may have poor performing IO or buffer pool memory pressure.