Anti Theft

I have just bought the explorer at an auction and had to change the belt tensioner, to do so I had to remove the battery, the car started fine after that but the next time I tried to start it, it flashed with Anti Theft and wouldnt start. It started again a few hours later but has not started again scince, it just keeps flashing anti theft. I only got the spare key with the sale not the remote key.

Can I dissarm the anti theft all together or bypass it!

I am to far away to get to an alarm specialist and they will charge a fortune for a tow!