Windows command line (CMD):
fsutil file createnew 1MB.xyz 1048576
fsutil file createnew 10MB.xyz 10485760
fsutil file createnew 50MB.xyz 52428800
fsutil file createnew 100MB.xyz 104857600
fsutil file createnew 500MB.xyz 524288000
fsutil file createnew 1GB.xyz 1073741824