Why is my mouse cursor dragging and slow and hesitates when connected to my wireless router only?

Hi,

1)   What type of a mouse are you using? Who is your device manufacturer?

2)   Do you recall making any changes to the computer prior to this issue?

3)   Is this issue confined only to a specific program?

Method 1: Boot the system in safe mode and check for the issue.

http://windows.microsoft.com/en-US/windows7/Start-your-computer-in-safe-mode

Please click on the link above and check for the steps to boot into safe mode.

Method 2: Put the computer in clean boot and test

How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7

http://support.microsoft.com/kb/929135 

Important: - Remember to put the computer back to normal startup follow step 7 in the link.

Check if the issue persists in clean boot state

Method 3: Optimize Windows 7 for better performance

http://windows.microsoft.com/en-us/windows7/Optimize-Windows-7-for-better-performance

Refer the above link and optimize Windows 7 performance.