Vista - Hard disk running constantly

I have Vista Business installed and have changed various things to have Vista
start and close quicker. It takes approx. 2½ minutes from I start my machine
until Vista is fully loaded. But after that the hard drive is running
constantly, which means it takes a long time to execute e.g. Excel. Can
someone tell me what I can do about that?

Hi,
a. Open "Task Manager" ( Ctrl+Shift+Esc )
b. Go to "Services" tab and select the "Services..." button ( right-bottom )
c. You maybe are prompt for a UA confirmation ( "Continue" ) [ Run as
administrator ]
d. The "Services" window
e. Search for "Superfetch" in [Name] column
f. Select it and then make a right-click ( mouse ) and choose from the list
- "Properties" item
g. At "Startup type:" [ "General" tab ] select it "Manual" and for "Service
status:" choose "Stopped" ( click on the "Stop" button )
h. Click "Apply" and see if there is a change in your hard-disk running mode;

Have a nice day!

In addition to what Bogdan has suggested, I would also disable the 'Windows Search' service.