This problem maybe you found, If you have just bought a brand new HP Pavilion dv2845se. The problem is Pavilion DV2845SE volume controls above the keyboard tend to freeze when displayed on the screen and it locks up whatever application you were in at the time. This DV2845SE using Microsoft Windows Vista Home Premium 64bit as Operating system.
Here is some step to solve this volume problem:
a. Go to search and choose “run” option
b. type msconfig
c. you have to locate Quick Touch On Screen Display
d. Please uncheck this Quick Touch On Screen Display Option
e. Click OK
Your problem will be solved after restart it.