if it happened like MrsD said, that you have installed it twice, what happened was that you've created more than one registry and they are now fighting each other. Then you'll have to delete the old registry and get to the newest like she suggested.

my suspicion is that you have run out of RAM and is not able to handle the memory of this program(may I ask what it is?). That's usually the first tell tale sign...the lack of memory...

if that isn't the case and you are able to download it, and you did download it more than once, then it becomes a registry issue..

that becomes a little bit more trickier and I'd try mrsD's suggestion.

do you have the specs on this program? It's usually in the back of the box under "sys requirements"

see what all the requirements are and see if your puter meets it. I think it might be the memory issue.