Yes but if the process is 64bit then the OS must be 64bit granted if the process is running 32bit under a 64bit OS then it would give a false value.
With VB its very easy to get information like this with a WMI call to Win32_Processor
AddressWidth: 32
Caption: x86 Family 6 Model 23 Stepping 7
DataWidth: 32
Description: x86 Family 6 Model 23 Stepping 7
AddressWidth, Caption, DataWidth, and Description are probably the most useful for processor achitecture, as i was testing that with a virtual machine i can only assume AddressWidth and DataWidth would report 64 under a 64bit Windows but i have no 64bit Windows installs here to test with.
Here... a quick Google search turns this up, it may save you asking so many questions.
http://vlaurie.com/computers2/Articles/environment.htm
C:\Documents and Settings\Administrator>echo %windir%
C:\WINDOWS
Edit:
Confirmed under Vista 64 the values for AddressWidth and DataWidth are 64.
Address Width: 64
Data Width: 64
Description: Intel64 Family 6 Model 23 Stepping 7
Note that the caption and description values are not always present so they may be a bad choice to rely on