Uninstall the 32-bit version. Install the 64-bit version. Take backups of the system databases and detach all user databases before then after you've installed the 64-bit restore the system DBs and attach the user DBs.
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)SQL In The Wild
: Discussions on DB performance with occasional diversions into recoverability
We walk in the dark places no others will enter
We stand on the bridge and no one may pass