Free windows optimizer and registry cleaner

My desktop is too slow.  I am looking to optimize my windows OS.

I would like to find a free registry cleaner and Windows Optimizer or whatever someone recommends to optimize my windows performance.

More details about my computer  

Component Details Subscore Base score
Processor AMD Phenom(tm) 9100e Quad-Core Processor 5.7 3.6
  Determined by lowest subscore
 
Memory (RAM) 4.00 GB 5.9
Graphics ATI Radeon HD 3200 Graphics 3.6
Gaming graphics 1919 MB Total available graphics memory 3.7
Primary hard disk 222GB Free (586GB Total) 5.9
Windows Vista (TM) Home Premium

System  
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  Manufacturer Gateway
  Model DX4200-09
  Total amount of system memory 4.00 GB RAM
  System type 64-bit operating system
  Number of processor cores 4
 
Storage  
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  Total size of hard disk(s) 586 GB
  Disk partition (C:) 222 GB Free (586 GB Total)
  Media drive (D:) CD/DVD
  Media drive (E:) CD/DVDCD/DVD
  Media drive (J:) CD/DVDCD/DVDCD/DVD
 
Graphics  
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  Display adapter type ATI Radeon HD 3200 Graphics
  Total available graphics memory 1919 MB
        Dedicated graphics memory 256 MB
        Dedicated system memory 0 MB
        Shared system memory 1663 MB
  Display adapter driver version 8.762.0.0
  Primary monitor resolution 1440x900
  Secondary monitor resolution 1440x900
  DirectX version DirectX 10
 
Network  
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  Network Adapter Marvell Yukon 88E8071 PCI-E Gigabit Ethernet Controller
  Network Adapter Microsoft Tun Miniport Adapter