Putting a tape measure on your lawn is a good idea. The deck may not have been properly set when it was assembled which would make the setting wrong, but you should not be having a problem with scalping unless it's cutting that low or the lawn is rough. Let us know if you are able to get your lawn striped. I didn't think of this earlier, but you mentioned you didn't know what type of grass you have. It's difficult to tell from the photos, but you can check with your local ag extension office or co-op and get some info. It may be that you have a type of grass that needs to be cut at around 2". As mentioned earlier though it's hard to stripe grass cut under 2".
samot,
The advice you're getting on cutting height to get good stripes is spot on!! I have mostly fescue with clover and some crabgrass:0( for my lawn. Even with a complete striping kit, I had been cutting at 2.5" with my deck heeled and not getting real "pronounced" stripes. Gravely recommended that I reset my deck pitch to the normal "forward pitch"(because I'm using a mulch kit) and to cut at 3" to get more pronounced stripes(the remaining grass blades have to be "tall enough" to bend...and stay bent... to reflect the sunlight properly for the dark/light striping look).
I too thought that cutting my lawn higher than 2" would make it look "uncut", but my father-in-law mows his at 4" with a Kubota ZTR and I must admit....it looks like a carpet!!! Ariens told me too many people cut their grass too short and for most grass types 2"-3" is the recommended minimum. It'll take a little getting used to cutting t a higher cutting height, but your grass will be healthier and if you continue cutting weekly it will "grow on you":0)
As an aside, you may want to find out what "type" grass you have. St. Augustine and other varieties are different than fescue or rye and user Ric posted a "chart" that showed recommended height ranges based upon grass type. I can't seem to find that thread right now:0(
Again, to get striping you would want to cut at the maximum recommended height for that grass type.