A. SQLHDTST.EXE is on your Technet CD and can also be downloaded from http://support.microsoft.com/download/support/mslfiles/SQLHDTST.EXE
This utility simulates SQL Server and stresses your disk and/or network connections. It should be run over an extended period (maybe a weekend) and will highlight any nasty intermittent hardware errors that may be causing corruptions, SQL hangs, crashes etc.
If it reports any errors then you have faulty hardware - which could be cpu, memory, disks, scsi controllers etc. If you can't track down the problem using hardware vendor tools then I would recommend swapping out the entire unit.