Ex has put himself as administrator on my computer

Question

I had my work computer in our home when I had to leave my husband and he refused to give it to me.  Well, before the judge finally made my exhusband return it he had taken me off as the administrator.  He had also hacked into my email accounts, facebook, changed my work access passwords, and all passwords to everything I had on my computer. It is against the law to do this but this judge didn't seem to care I guess because this wasn't a criminal hearing. But he did finally make him give me my computer. 
My issue is he has locked me out of everything!  I can only access it as a guest with no control and can make no changes.  I cannot download a program without his name popping up with the request for the password so what programs I need to work I can't use after I down load them.  I cannot make a new user name, no changes to the appearance, no personalizing, to configuring, testing, no downloads will be accessable without his code, will not display current owner name, will not show ram, even the processor name has been made unavailable, will not show installed RAM, credentials for automatic log in, all three disabled and inaccessable by adminstrator, cannot even open parent controls, windows cardspace rendered in accessable, so you get what I am saying.  He isn't that smart so he had help to do this.  Also can not use restore, and can not go back and restore to factory status we tried he has done something to block access as the administrator there as well.  He has also done this not only out of a controlling abusive individual but he is also afraid something he has done on my computer while in his hands will be found in the computer.  We are divorced now and that doesn't matter as much anymore but he still will not relinquish control and I can not afford to take him back to court to make him give me the password.  It is so hard I am desperate for real help.  I have researched on line and tried things but administrative control is everywhere.
He has kept all the paperwork and CD's.  It is an HP TouchSmart IQ500 Series PC, with an Intel Core 2, Duo, with Windows Vista operating system and I got it in 2009. 
When you reply, please give me very detailed instructions because I have found when I was online getting instructions from people they always seem to leave out something they thought was minor or was assuming I would automatically know what to do next.  It took forever to get it right and nothing obviously worked.  I refuse to give up I know someone has to know what to do.  Surely you don't through away a computer because of a password.
Thank you in advance for your immediately responses. 

Answer 1

Warning as always research programs and websites before downloading.  Scan downloads for viruses before using.
I have personally used the Ntpasswd to bypass the password when I cannot access a computer a relative or friend asks to repair/fix issues.  The program can be found here.
http://pogostick.net/~pnh/ntpasswd/
To use this program you need access to BIOS setup, to check for that when you boot the computer the screen might show something like below.
http://bizsupport1.austin.hp.com/bizsupport/TechSupport/Document.jsp?objectID=bph07110&lang=en&cc=us...
If can either install the program on a USB stick or DVD/CD disc.   The appropriate device is chosen in step 4 below
Once you have access to the above you need to set the Boot order( choosing what computer uses when turned on, ie Uses the Hard drive, usb stick, or dvd drive )
Steps to change boot order    Note the directions might differ for you computer because Bios Setup is different for each computer often
Once in the BIOS setup, press the right arrow key til you reach the "Boot" tab
Press down arrow key til you reach "Boot Priority"
Press enter
Select USB or DVD drive and press enter
Move the highlighted item (USB or DVD drive) to the top of the list and press enter
Press the F10 key and select the "Save and exit" option, press enter
This change basically allows you to  run anything on a USB stick or DVD drive before Windows starts running on your computer.
Try changing the boot order and post back if you can do that.  If it's not possible to do you might need to contact HP or whatever store you bought the computer from.