Actually a Compaq laptop we have doesnt have IrDA, it has standard IR for a remote control - i checked this with HP, as it cant do data. What is your laptop model, yours might be a similar case.You can use IR with your laptop, just not with the built in IR port.
The IR system that laptops, PDAs and mobile phones use is called IrDA and it's not the same as the Consumer IR methods that tv remotes use.
IrDA has a maximum range of about 1 metre, but usually it only works for about 30 centimetres.
I haven't seen any Windows software that can use IrDA for remote controls, but I know there has been a very small amount of success in doing it on Linux.
You're better off trying to use something like Bluetooth, Wi-Fi or just buying a USB IR Receiver.
Does the laptop have Bluetooth or Wi-Fi? Because there are remote programs you could run on your PDA that would work over one of those.
Hope that helps,