|First step would be to run your virus scans.|
Clear your temporary internet files from within IE.
If there is room try MalwareBytes freebie too.
How large are your hard disks and how much free space is showing on them?
Various updates can eat away at your hard disk space but this usually happens quite slowly.
Even Defrag might help a tad for now.
If one of the HD's (D probably) is just for data or backups then you can turn off system restore for that disk to save some space.
Please do not post then vanish - let us know the outcome