How can I get my external hard drive back to its original size-->200gb?

I mistakenly used my external hard drive as the destination for a clone. Now it's a measly 37.2gb (the size of the source disc/an old IDE hard drive). I'm using Acronis software and I thought I was simply making a clone file I could then use to make another IDE HDD. I'm going to use a new IDE HDD and a double ribbon cable now for the clone but how can I get my external hard drive back to the original 200gb as it was before?