1st thing I would do is check the system files:
Open a Command Window in Administrator mode:
* click Start
* click All Programs, then Accessories
* right click on the Command Prompt option,
* on the drop down menu which appears, click on the Run as Administrator option.
* If you haven’t disabled User Account Control (and you shouldn’t!) you will be asked for authorization. Click the Continue button if you are the administrator or insert the administrator password.
2. Start the System File Checker
* In the Command Prompt window, type:
sfc /scannow,
* press Enter.
* You’ll see “the system scan will begin”.
The scan may take some time and windows will repair/replace any corrupt or missing files. You will be asked to insert your Vista DVD if it’s needed.
Close the Command Prompt Window when the job is finished.
Next I would:
Run malwarebytes
Then I would:
Turn off automatic defrag
Having a well de-fragmented disk improves performance, but background defragmenting can slow your machine down temporarily. Vista schedules disk defragmenting by default. However, you may need to use your PC while it's carrying out this task. You can do this, but there'll be a performance hit.
If this is likely to be a problem, turn off scheduling by launching Disk Defragmenter, then clearing the box marked 'Run on a schedule (recommended)'. You'll need to run Defragmenter manually, so remember to do it once a month
Optimise SATA hard drives
Most PCs running Windows Vista will have SATA hard drives installed. If yours does, you can improve its performance by enabling Advanced Performance on the drive.
Do this by launching Device Manager (click 'Start', right-click 'Computer', select 'Properties' and then choose 'Device manager' from the left-hand pane) and expanding 'Disk drives'. Right-click your SATA drive and then choose 'Properties'. Move to the 'Policies' tab.
Write caching should already be enabled on the disk, but you'll need to tick the 'Advanced Performance' box.
Remember, you should only apply this change on laptops with batteries, or desktop PCs with uninterruptible power supplies, because it's possible to lose data during a write operation if there's a power failure.
Identify problems with a System Health Report
In Control Panel, choose 'System and maintenance | Performance information and tools | Advanced tools'. Click 'Generate a system health report' and select the option to continue if prompted.
The tool collects information from the Reliability and Performance Monitor to make the report. This lists potential problems like low disk space and suggests fixes.
Try Disable Transparency
Right click your desktop
Select Personalize
Choose Windows Color And Appearance
Uncheck Enable Transparency
Click OK
Disable the Animation for Minimizing and Maximizing Windows
Go to Control Panel
Click System and Maintenance
Select Performance Information and Tools
Click Advanced Tools
Click Adjust The Appearance and Performance of Windows
Uncheck all of them except for Use Visual Styles on Windows and Button
Download and run
CCleaner - Free One
https://www.ccleaner.com/ccleaner/download