Woah... slow down a bit...
Assuming that you're using RH9.0 which you stated in your distribution info, AND assuming that you never upgraded your kernel at all (because your particular device is definitely supported in the 2.6 kernel series), here's what I suggest you to do (note: do all this as root).
Go to the dir where you compiled the module, and do this: gzip astir4200.o
...a file called astir4200.o.gz should be seen there after running that.
After that type: uname -r
...this will return your kernel build info. Note this down.
After that type this: cp astir4200.o.gz /lib/modules/(the value returned by uname -r)/kernel/driver/net/irda/
- DO NOT KEY IN THE PARENTHESIS.
After that, just type modprobe astir4200
... the module for your infrared device should now be loaded... How you use it is a totally different matter, don't ask me about that... I never used an IRDA gadget under Linux my whole life