On my laptop I downloaded Helium Hydra for Windows 64 bit OS. After running the monero-wallet-gui.exe and waiting for the syncing to stop (about 15 hours) I suspect about 30GB of C:/ space was used. I wasn't keeping exact track of my hard drive space but I'm fairly sure running the exe and syncing took up a lot of space. If monero-wallet-gui.exe has taken up this disk space how do I reallocate it? I've exited the GUI and stopped the service. I've done the disk clean up and also run CCleaner. A disk analysis of what's taking up space didn't reveal anything remarkable. (I'm planning to move my wallet off my laptop's hard drive and to an external drive.)
The Monero blockchain data is located (for Windows) at C:\ProgramData\bitmonero\lmdb
If you want to be able to view your wallet's balance, etc., you will need to move the entire blockchain onto an external drive, not just your wallet. Definitely have a look at this question by debruyne for help on trying to move the blockchain data without losing sync progress. .