Hi Tom,
Was your Hero supplied via Orange or a reseller? Depending on whether it was branded or not, go to
here and download either the Orange or the generic 2.73.xxx.xx update. Connect your handset to the PC and run the update utility to return your handset to a completely stock state. It will be totally wiped in the process so ensure you have necessary backups. The external memory card is unaffected and data there is safe.