Try this program and see if it will work. I have it but don't use it much, really it's more because I don't know much about it. But I think it will do what you want. Also if you use Photoshop CS3 I think it will do it as well but I don't own CS3.
http://epaperpress.com/ptlens/

I am assuming you are using a coolpix nikon fisheye lens

Open PW5, 

Image type : Circular Fisheye  and tell it 1 image only

Load your 1 fisheye image

and Stitch the 1 image panorama.  What Panoweaver will do is DEwarp the image to say a 2000 x 2000 pixel flat image.

When I tried.. it dewarped the full circle image (canon 5d and full circle Sigma 8) alright.. but the door frames and angles came out bit odd.

After dewarping the fe image, and if you have Photoshop CS3 there is an option item tool called   EDIT |  TRANSFORM | WARP  and PS puts a grid overlay on the image.. and you can drag the doorway edges vertical.

What would I do? On my first site visit I would take my little pocket Canon powershot 10mpixel point and shoot  and use it.  Other wise I would take your E-63  24mm wide angle lens back to the site and reshoot.