It's easy to get the Restoration Disk/s for an HP computer, Margaret.
May be able to guide you on here with repairing your computer also, and leave the 'GEEKS' at Best Buy to twiddle their thumbs, and make money off of someone else.
On the back of your Compaq Presario SR1500NX Desktop PC, is a white sticker.
You need to write down the Serial Number, to give to the nice representative on the phone, for HP Support.
(ONLY give out to an authorized HP representative. Do NOT post on a world-wide forum such as this)
S/N = Serial Number
In the USA call the toll free phone number - 1-800- 474-6836
24 hours a day, 7 days a week.
The Restoration Disk is free. The shipping and handling is not.
$17 for a 5 to 7 day ship, $24 for a 2 to 3 day ship.
Not in the USA?
Use HP Support Worldwide,http://www8.hp.com/us/en/hp-information/summary/ww-support.html
When you receive the Restoration Disk/s, turn the computer on, put the disk in the optical drive's tray. (CD/DVD Drive)
Drive closed let the disk load.
WHEN asked click on - Repair (Non-Destructive Installation)
This will repair the basic Windows files.
IF, you have a virus, AND cannot get rid of it, you'll have to take the computer back to Day 1, when it came from the factory.
This will be a Full Install. (Destructive Installation)
ALL of your personal information, AND any programs you have installed, will be GONE!
The computer will be back to Day 1 from the factory, and before you put anything on it.
For additional questions please post in a Comment.
(Sound like I'm being harsh with Best Buy, and Geek Squad?
I, and others on FixYa, have repaired OODLES of problems made by these guys! )