Ok, it works! I used C:\Program Files\NCBI\blast-2.2.28+>makeblastdb -in test_gene.txt -title test_gene -dbtype nucl -out test_gene and I got the same stuff as before, but with 'Adding sequences from FASTA; added 1 sequence in 0.000725742 seconds. on the end instead of the error message.
Now the only problem is that I don't know where the computer put the database file. I can't find it anywhere. I typed in C:\Program Files\NCBI\blast-2.2.28+>dirand the database isn't there. I also made it so i can see hidden and system folders and files, but it isn't there either.
Edit: Found it. It was in C:\Users\Evan\AppData\Local\VirtualStore\Program Files\NCBI\blast-2.2.28+ It's listed under 3 files: test_gene.nhr, test_gene.nin, and test_gene.nsq. I found it using C:\>dir test_gene* /s /p in the command line.