Translation help with hairu/ireru

Hello, I would really appreciate some help with the following sentence. The speaker is watching a movie, and he explains that he just bought the DVD online. (I think)

気まぐれのネット通販で手当たり次第入れたら入ってた

気まぐれ and 手当たり次第 are not expressions I'm familiar with. I looked them up, but my knowledge of Japanese is only low-intermediate. So, did the buying of this movie occur in a very, very haphazard fashion?

And then the conditional + transitive/intransitive thing at the end of the sentence is terribly confusing to me.
If someone could please explain to me what is going on I would be very grateful.
Thanks!

Break up the sentence and enter here:
http://ejje.weblio.jp/content/%E6%B0%97%E3%81%BE%E3%81%90%E3%82%8C
You will see the forms, translations & sample usages.

I'd say it was not just that he "bought" a DVD online, but probably that he (is this a really rare DVD or something?) entered his application to purchase/entry into lottery, then he found out that he was selected ("in") (thug was able to buy), or something like that. Without the background, this sounds quite strange.

It sounds something like:
- Following my whim, I just submitted (my application to purchase) on internet mail-order shops just as many as I found them, then I (my order) was in.

入れたら iretara is conditional of 入れる ireru, to enter (something), to submit (an application), place in (something), etc.
入ってた haitteta is short form for 入っていた haitte ita. THe original verb is 入る hairu, for (someone/something) to come in,
　

気まぐれのネット通販で手当たり次第入れたら入ってた。

ネット通販 [netto tsuuhan] means sails via Internet. Here a word to mean a shopping is omitted.
And 入れる [ireru] in this sentence can be understood
as 品物を買い物かごに入れる [shinamono wo kaimono-kago ni ireru]
( = put goods into a shopping basket).

気まぐれのネット通販で手当たり次第に入れたら、このDVD が入ってた。
: Shopping on a whim on the Internet / the web, I put into my basket every item I noticed, resulting in this DVD's coming in (i.e. resulting in my getting this DVD).

AK: 入れる ireru, to enter (something), to submit (an application), place in (something), etc.

To say submitting an application, I suppose 出す [dasu] is used more often, which means putting out.
出す can be used without the place to which or the person to whom one submits.
入れる [ireru] usually accompanies the place to put into, which also can be omitted if obvious or needless to say.

Note that 入れる [haireru] is another word. It means, so to say, can + 入る [hairu].

この合唱団にはあと一人､入れます [Kono gasshou-dan niwa ato hito-ri haire-masu]。
: One more person can get admission to this chorus.
/ One more person can take place in this chorus.
/ This chorus has room for one more member.

気まぐれ and 手当たり次第 are not expressions I'm familiar with.

気まぐれの散歩 [kimagure no sampo]
: a stroll on a whim
気まぐれに散歩する [kimagureni samposuru]
: have a stroll on a whim
気まぐれな天気 [kimagurena tenki]
: capricious / changeable weather

手当たり次第 is a short expression of 手当たり次第に [teatari-shidai-ni].
It's not always easy to translate this phrase, which literally means something like "in the order of one's hand touches" or "each time it comes to one's hand" or so.
The English phrase "in a haphazard fashion" is nice in meaning "without a particular order"
but does not always imply "any item one finds" or "as many items as one can find," which 手当たり次第に can imply.

I put into my basket every item I noticed,

"I encountered" sounds better than "I noticed."
Here "I" had picked up this DVD without intention, which was by chance included in the items "I" ordered.

Thank you all very much!

Especially omotenashi, your thorough explanation was wonderful! Very helpful and informative.