Cory is absolutely correct. Be extremely careful as to which hidden files you "play with". As long as you "isolate" the particular .RAR file, you should be OK. By the way, what type of application is associated with the .RAR file?
And, his statement about making a backup is critical! In fact, the lack of a backup seems to be a problem/issue with quite a few folks around here. I can't tell you how many times (especially recently) a backup "saved my bacon", so to speak! If you use Time Machine, just remember that it does not make a bootable backup, and recovery is somewhat more challenging (but doable). In essence, a complete recovery would involve 1) Erasing, formatting, and partitioning your internal drive, 2) installing whatever version of the Mac OS you are using (including updates), and 3) using Migration Assistant to bring over non-OS files/folders, etc. from the Time Machine backup. If instead you use a backup/cloning program like SuperDuper! or Carbon Copy Cloner, either one makes a bootable backup/clone of your system. If you need to recover, you woudl boot your machine from the backup. You would still do #1 (either program can do that for you, but I prefer to have Disk Utility do it), and then just restore everything (OS and all) from that backup.