I forgot my windows vista aministrator password

I have an acer aspire 5720 laptop with windows vista that is working fine. But I forgot my windows vista administrator password and I can not install any software and I cannot even use system restore. For recovering or bypassing my administrator password I tried the "free" WINDOWS PASSWORD RESCUER, but almost at the end It gave me the message: THE FREE VERSION CAN NOT RECOVER THE ADMINSTRATOR PASSWORD. yOU HAVE TO PURCHASE THE FULL VERSION WINDOWS PASSORD RESCUER.

So my question is: For recovering or bypassing the administrator password do I have to buy software, or is there another free way to do that?

I appreciate any information, the more the better for me. Sincerely, oldenter 62.