It can give you a couple of frames if you have a better HDD but it is usually minimal. i have a velociraptor 80gb and it tears my 1tb drive a new one when it comes to opening any program or loading screens. that is the biggest difference though.
Hard drive has no effect on fps for gaming.
Velociraptor was good in it's time. the 10K rpm made for faster access times.
That made it a very good drive for the OS because the OS does lots of small random i/o operations.
Because it is not as dense as the newer >1tb hard drives, it is actually slower in sequential data rates.
It is those sequential data rates which might be of benefit to level loading times for games.
By far, the best for gaming is a SSD.
As an OS drive, it will do random I/O 50x faster than the VR.
It will do sequential I/O 2-3x faster than the fastest hard drive.
The main drawback is cost. Expect to pay $2 per gb.
You should look at a 60gb SSD for the OS, but a 120gb SSD will let you keep a few current games on it. Use a large 1tb drive for storage and overflow.