Can you....

[Bimbalbamble]

.... Download a file (music album for instance) on your iMac, save it to your a
formatted external hard drive for a Mac BUT somehow use it on a windows Laptop?

I will only be using the laptop to run a one programme only for work and just need to access the music files on the HD

 

[miles01110]

Not if the drive is formatted as Mac OS Extended (Journaled). It'd need to be NTFS or FAT.

 

[Vylen]

Mac OS Journaled(HFS+) partitions can be accessed via Windows using either MacDrive (commercial) or HFSExplorer (open source).