Wir archivieren das Fotoalbum auf der Festplatte.

Because archivieren is conjugated for wir (we).

The infinitive is archivieren. In the present tense:

• ich archiviere
• du archivierst
• er/sie/es archiviert
• wir archivieren
• ihr archiviert
• sie/Sie archivieren

So wir archivieren means we archive. With wir, many German verbs use the same form as the infinitive.

Yes. archivieren is a regular verb in German.

That means it follows the normal present-tense pattern and forms its past participle in the usual way:

• infinitive: archivieren
• present: wir archivieren
• simple past: archivierte
• past participle: archiviert

Example:

• Wir haben das Fotoalbum archiviert. = We archived the photo album.

Because Fotoalbum is a neuter noun in German, so its article is das.

• das Fotoalbum = the photo album

In this sentence, das Fotoalbum is also the direct object, and the neuter article in the nominative and accusative singular is the same: das.

So here:

• Wir = subject
• archivieren = verb
• das Fotoalbum = direct object

It is the thing being archived, so it is the direct object.

A useful way to spot it is to ask:

• What are we archiving?
• Answer: das Fotoalbum

That makes das Fotoalbum the accusative object.

Sentence structure:

• Wir = subject
• archivieren = verb
• das Fotoalbum = accusative object
• auf der Festplatte = prepositional phrase telling you where

Because auf is a two-way preposition, and here it is used in a location sense, not a direction/movement toward a destination sense.

Two-way prepositions like auf can take:

• dative for location: where?
• accusative for direction/destination: where to?

Here, auf der Festplatte means something like on the hard drive as the storage location, so German uses the dative:

• auf der Festplatte

Compare:

• Das Fotoalbum ist auf der Festplatte. = The photo album is on the hard drive.
• Wir kopieren das Fotoalbum auf the Festplatte. Actually correct German: Wir kopieren das Fotoalbum auf die Festplatte. = We copy the photo album onto the hard drive.

In your sentence, the focus is the result/location of storage, so auf der Festplatte is natural.

Because Festplatte is a feminine noun, and after auf in the dative case, the feminine article changes:

• nominative: die Festplatte
• accusative: die Festplatte
• dative: der Festplatte

So:

• die Festplatte = the hard drive
• auf der Festplatte = on the hard drive

This is a very common pattern with feminine nouns:

• in der Schule
• an der Wand
• auf der Festplatte

This is one of those places where German and English use prepositions differently.

In German, storage media are very often described with auf:

• auf der Festplatte = on the hard drive
• auf dem Computer = on the computer
• auf dem USB-Stick = on the USB stick

Even if English sometimes uses in or on depending on context, German commonly prefers auf for these devices/media.

So the sentence sounds natural in German, even if a learner might expect in.

The word order is the normal German pattern for a main clause:

subject + verb + object + additional information

So:

• Wir = subject
• archivieren = finite verb
• das Fotoalbum = object
• auf der Festplatte = prepositional phrase

German main clauses usually put the conjugated verb in the second position. That is exactly what happens here:

• Wir archivieren das Fotoalbum auf der Festplatte.

You could move another element to the front for emphasis, but then the verb still stays second:

• Auf der Festplatte archivieren wir das Fotoalbum.

It is possible in some contexts, but it changes the feel.

• auf der Festplatte emphasizes the storage location: on the hard drive
• auf die Festplatte emphasizes movement/transfer onto it: onto the hard drive

So if you are talking about the act of transferring the file to that destination, auf die Festplatte can make sense with verbs like:

• kopieren
• laden
• speichern

For archivieren, auf der Festplatte is very natural when you mean the album is archived there.

Exactly. German often combines nouns into one compound word.

Here:

• Foto = photo
• Album = album
• Fotoalbum = photo album

English usually writes this as two words, but German commonly writes such combinations as one word.

This is very typical in German:

• Hausaufgabe = homework
• Krankenhaus = hospital
• Bücherregal = bookshelf

Because all nouns are capitalized in German.

So in this sentence:

• Wir is capitalized because it starts the sentence
• Fotoalbum is capitalized because it is a noun
• Festplatte is capitalized because it is a noun

This is a standard rule in German and one of the easiest ways to spot nouns when reading.

Yes, archivieren is perfectly possible, especially if you mean to archive in the sense of storing something systematically or for long-term keeping.

But depending on context, other verbs might also be common:

• speichern = to save
• sichern = to back up / secure
• ablegen = to file / store
• speichern auf der Festplatte = save on the hard drive

So:

• Wir archivieren das Fotoalbum auf der Festplatte. suggests organized or archival storage.
• Wir speichern das Fotoalbum auf der Festplatte. is a more everyday way to say we save the photo album on the hard drive.

A common conversational past form would be the Perfekt:

• Wir haben das Fotoalbum auf der Festplatte archiviert.

A simple past form is also possible, though less common in everyday spoken German for this kind of verb:

• Wir archivierten das Fotoalbum auf der Festplatte.

For most everyday speaking, learners will hear and use haben + past participle much more often.