Learn English – word for someone who is a regular computer user but not an expert

Discontent or discontented could easily fit.

Here is a list of several words that are somewhat synonyms to this concept, and depending on context might prove useful:

blue, complaining, crabby, disgruntled, displeased, disquieted, exasperated, fed up, fretful, griping, perturbed, picky, restless, ungratified, upset, vexed

It depends partly on how active the discontentment is. Exasperated, griping, crabby, etc, have connotations of outward display of discontentment, while blue, discontent, disgruntled, etc can be relatively contained.

Restless presents an important nuance: it does not have to be negative. This is a valuable word to use when the discontentment is not a bad thing, especially when there is hope of resolving the cause of restlessness.

Perfectionist might be a helpful word (also maybe stickler or idealist); this describes someone who can't relax until the thing he/she is working on is perfect.

The word you are looking for is SYSYPHEAN. Although rarely used it refers to the legend of Sysyphus, a man punished by the gods by attempting to roll a rock up a hill. No matter how he tried, the rock would roll back down the hill and he would be forced to start over. Used in a sentence it would be; Joe's many attempts at a business were sysyphean since they inevitably failed.