to check Windows for 32-bit OS or 64-bit OS :

Start --> Run --> msinfo32.exe

System Type :

• For 32-bit editions of Windows : x86-based PC.
• For 64-bit editions of Windows : x64-based PC.

OS Name    Microsoft Windows XP Professional
Version    5.1.2600 Service Pack 3 Build 2600
OS Manufacturer   
System Name    
System Manufacturer    
System Model   
System Type    X86-based PC
Processor    x86 Family 6 Model 15 Stepping 13 GenuineIntel ~1994 Mhz
BIOS Version/Date    COMPAL 1.16, 12/31/2007
SMBIOS Version    2.4
Windows Directory    C:\WINDOWS
System Directory    C:\WINDOWS\system32
Boot Device    \Device\HarddiskVolume1
Locale    
Hardware Abstraction Layer    Version = "5.1.2600.5512 (xpsp.080413-2111)"
User Name    
Time Zone    GTB Daylight Time
Total Physical Memory    2,048.00 MB
Available Physical Memory    1.03 GB
Total Virtual Memory    2.00 GB
Available Virtual Memory    1.96 GB
Page File Space    3.84 GB
Page File    C:\pagefile.sys