If running Workstation 5.5 or 6.0, when client creates a VM using the New Virtual Machine Wizard, there is a list of Operating Systems on the Guest Operating System page; choose one of the 64bit OS editions from this list (Note: Do not try to install a 64bit OS on a VM that was created using a 32bit OS from this menu). Then the guest install is as usual. Also be sure to note the restrictions below for hardware and supported Guest OSes. If running a version earlier than 5.5, client needs to upgrade if they need 64 bit support.

Need one of the following processors: (See the following link for information on certifying the processor as compatible. http://www.vmware.com/pdf/processor_check.pdf)

# AMD™ Athlon™ 64, revision D or later
# AMD Opteron™, revision E or later
# AMD Turion™ 64, revision E or later
# AMD Sempron™, 64-bit-capable revision D or later (experimental support)
# Intel EM64T VT-capable processors (experimental support)

Also need to run one of the following guest OSes:

Added in 6.0 or greater:
# Windows Vista Enterprise
# Windows Vista Enterprise (3‐D effects not yet supported)
# Windows Vista Business (3‐D effects not yet supported)
# Windows Vista Home Basic and Premium (3‐D effects not yet supported)
# Windows Vista Ultimate (3‐D effects not yet supported)
# Windows Server 2008
# Red Hat Enterprise Linux 4.5
# Red Hat Enterprise Linux 5.0
# SUSE Linux Enterprise Server 9 SP4
# SUSE Linux Enterprise Server 10 SP1
# openSUSE 10.2 (formerly known as SUSE Linux 10.2)
# openSUSE 10.3
# Turbolinux 10 Server
# Solaris x86 10 Update 3
# Ubuntu Linux 6.10
# Ubuntu Linux 7.04
# Mandriva Linux 2007
# Mandriva Corporate Desktop 4.0
# FreeBSD 6.2

5.5 or greater
# Windows Server 2003 x64 Edition SP1, R2
# Windows XP Professional x64 Edition
# Mandriva Linux 2006
# Mandriva Corporate Server 4
# Experimental support for Mandriva Linux 2007
# Red Hat Enterprise Linux AS/ES/WS 4.0, 4.0 Update 3, 4
# Red Hat Enterprise Linux AS/ES/WS 3.0, 3.0 Update 2.4.21-15, 6, 7, 8
# Experimental support for Red Hat Enterprise Linux AS/ES/WS 5.0
# SUSE Linux Enterprise Server 9, 9 SP1, 9 SP2, 9 SP3, 10
# SUSE Linux 9.1, 9.2, 9.2 SP 1, 9.3, 10, 10.1
# Ubuntu Linux 5.04, 5.10, 6.06
# Experimental support for Ubuntu Linux 6.10
# FreeBSD 5.3, 5.4
# Experimental support for FreeBSD 6.1
# Experimental support for FreeBSD 6.0
# Experimental support for Solaris x86 10 1/06 (Update 1) and Solaris x86 10 6/06 (Update 2)