I tried this (PS2) as both a restricted user and administrator and I get the same results.
I am using Win 7 with Powershell 2.0.

When I view with RegEdit the key and it's default value of '1' exist.
Using fsutil, it exists with it's default value:

C:\windows\system32>fsutil behavior query DisableLastAccess
DisableLastAccess = 1

If I use Powershell to query:

Get-ItemProperty HKLM:\System\CurrentControlSet\Control\FileSystem\

I get the full list of subkeys and values:

PSPath                                : Microsoft.PowerShell.Core\Registry::HKEY_LOCAL_MACHINE\System\CurrentControlSet
                                        \Control\FileSystem\
PSParentPath                          : Microsoft.PowerShell.Core\Registry::HKEY_LOCAL_MACHINE\System\CurrentControlSet
                                        \Control
PSChildName                           : FileSystem
PSDrive                               : HKLM
PSProvider                            : Microsoft.PowerShell.Core\Registry
DisableDeleteNotification             : 0
SymlinkLocalToLocalEvaluation         : 1
SymlinkLocalToRemoteEvaluation        : 1
SymlinkRemoteToLocalEvaluation        : 0
SymlinkRemoteToRemoteEvaluation       : 0
Win31FileSystem                       : 0
Win95TruncatedExtensions              : 1
NtfsAllowExtendedCharacter8dot3Rename : 0
NtfsBugcheckOnCorrupt                 : 0
NtfsDisable8dot3NameCreation          : 2
NtfsDisableCompression                : 0
NtfsDisableEncryption                 : 0
NtfsDisableLastAccessUpdate           : 1
NtfsDisableVolsnapHints               : 2
NtfsEncryptPagingFile                 : 0
NtfsMemoryUsage                       : 0
NtfsMftZoneReservation                : 0
NtfsQuotaNotifyRate                   : 3600
UdfsCloseSessionOnEject               : 3
UdfsSoftwareDefectManagement          : 0

which includes the single subkey I am interested in:
NtfsDisableLastAccessUpdate           : 1

When I try to query just that subkey, the response is as if it doesn't exist:

PS C:\windows\system32> Get-ItemProperty HKLM:\System\CurrentControlSet\Control\FileSystem\NtfsDisablelastAccessUpdate

Get-ItemProperty : Cannot find path 'HKLM:\System\CurrentControlSet\Control\FileSystem\NtfsDisablelastAccessUpdate' bec
ause it does not exist.
At line:1 char:17
+ Get-ItemProperty <<<<  HKLM:\System\CurrentControlSet\Control\FileSystem\NtfsDisablelastAccessUpdate
+ CategoryInfo          : ObjectNotFound: (HKLM:\System\Cu...astAccessUpdate:String) [Get-ItemProperty], ItemNotFoundException
+ FullyQualifiedErrorId : PathNotFound,Microsoft.PowerShell.Commands.GetItemPropertyCommand


I will be grateful to learn where the error in my attempt is.

Thank-you,
 --Bruce D. Meyer

Like this:
Get-ItemProperty -path HKLM:\System\CurrentControlSet\Control\FileSystem -name NtfsDisablelastAccessUpdate

Thank-you Marco,
It looks like I need to read up on the syntax.
--Bruce