I would greatly appreciate it if anybody could help me with this issue.

2003 stock s2000 with compustar alarm system with 8k miles.

So I left my car sitting in the garage for a good month and a week. I got in the car and nothing would start up.... nothing at all. I decided to get a new battery since I figured the original battery was about due time. So I get a new battery and throw it in the car... soon as I hook it up the horn goes off (probably because of my alarm).. so I take the fuse out of the horn and plug the battery connection back up.... i hear something spooling up, but the car does not start up... like nothing will turn on.... I thought maybe it was a kill switch for the alarm I got installed, but the car stereo guys that installed the alarm said that my particular alarm doesnt have a kill switch that needs to be pressed after a battery change.

I was thinking next step would be to check the fuses, but I cant get to them until i get back from this business trip im on right now. Does anybody else know what could be the issue? I would greatly appreciate any help. Thank you!

Jorge