Photoshop help

[JAS]

I have stacked my first ever set of frames in Dss from my cannon 1100D, 52 lights and 20 darks.

The file has saved as a 8580 x 5712, 455mb tif file.

When I try to open it, photoshop says it can not open the file there is not enough memory (ram).

Do I need to change some settings in DSS to creat a smaller file?

Or have I got somthing else wrong.

My laptop has a dual core pentium T4200 2ghz 3mb ram 32bit, windows 7.

Thanks in advance.

Jason.