partitioning - Can I move the start of non-boot partition safely after shrinking Windows partition?

Partition details (1 TB hard drive):

┌───────┬───────┬──────┬──────────┬────────────────────────────────────┐
│ Drive │ Total │ Free │ Free (%) │              Contents              │
├───────┼───────┼──────┼──────────┼────────────────────────────────────┤
│  C    │    93 │   67 │    72    │ Windows; few apps                  │
│  D    │   840 │  374 │    45    │ Docs, music, movies, portable apps │
└───────┴───────┴──────┴──────────┴────────────────────────────────────┘

Recently, I decided to have portable versions of almost all the applications I use. So, that resulted in a lot of free space in C drive, and I'm thinking of shriking it to make D drive bigger.

Can I be 100% sure that it'll be safe to expand the D partition (which doesn't contain system files) by shrinking C partition and moving the start of D?

Will it affect the portable apps I'm using?

Answer

It will be rather safe. It shouldn't affect anything.

Rather, because partition operations always come with a risk - for example due to a power failure or a software bug. So make backups unless you can take the risk of losing that partition.

Windows' built-in Disk Management won't let you move a partition, you'll have to use a 3rd party tool. I personally boot from an Ubuntu flash drive and use GParted to move partitions.

NTFS partitions can't be "simply" resized left. Your partitioning tool of choice will have to copy its contents to the new location, then extend it right. This will take some time.