Backing up to a memory stick is perfectly feasible, provided you leave the stick in the same USB port at the required times. The operating system will remember the precise location of the drive to which you first backed up, and will look for it each time.

As far as the ticking noise is concerned, it may well be indicative of a pending hard drive problem, so data backup is essential. Your software isn't such a problem, as Chronus says. Provided you have licence keys for downloaded applications you will usually be OK,although some software companies put a time limit on repeat downloads.

Your computer may simply be ticking as it heats or cools - does the noise happen at regular intervals? One way to check whether it's a hard drive issue is to close all running applications and simply let the computer rest. don't touch the mouse or keyboard, and sit there with a cup of coffee - just listen. The hard drive will spin down and park its read/write heads, and you should hear nothing. If you still hear the ticking noise it's less likely to be a drive problem. I say 'less likely' because the drive may be accessed by the operating system when you're doing nothing.

See if this is any help http://datacent.com/harddrivesounds.php

Sorry I cant get the link to work, you could type it in your browser. It give examples of noises made by failing hard drives or you could just type in "hard drive noises" there are other sites.