Full Detailed Walkthrough...

The Courier will approach you and give you a Dawnstar Museum pamphlet. (You must be at least level 20 for this to happen). Head to Dawnstar and go to Silus Vesuius' house. He will offer you a tour of the museum, and after the tour he will ask you to retrieve the three pieces of Mehrunes' Razor.

The hilt is in Morthal. When you meet Jorgen, the keeper of the hilt, he will deny knowledge. Convince him you know he has the hilt, and he will refuse to give it to you. Threaten, persuade, or pay him to gain access to the hilt. It is in a locked chest in his house to the west of the mill, so feel free to take it without even talking to him.

The shards of the blade of Mehrune's Razor is held in the vault of the basement of Cracked Tusk Keep. The key to the vault is on the bandit chief boss "Ghunzul". A hidden button on the wall opens the gate to the locked door opened by the key. Inside the vault, there are no enemies, but the way is trapped. A levers to the left and right of the pedestal open the 2. The "Become Ethereal" shout will let you run through the traps.

The pommel of Mehrune's Razor is at Dead Crone Rock. You will need to proceed through a series of tiers (in and out of the ruin) before reaching a hagraven at the very top who has the pommel. There is also a word wall nearby. You may find it necessary to walk all the way up to the word instead of standing slightly back as usual.

After retrieving the three pieces return to Silus and he will pay you a leveled amount of gold (more if brought all at once) and then ask you to meet him at the Shrine to Mehrunes Dagon. Upon arrival, he will be unable to get Dagon to repair the Dagger, so he will ask you to interact with the shrine. At this point, the daedric prince will demand that you kill Silus. Silus will ask you to spare him in return for 500 gold, saying that he will place the pieces of the Razor in a display case in his house. If you accept, he will give you the gold and run back to his house taking the broken dagger with him, while Dagon summons two Dremora to kill you.

If you choose to kill Silus, interact with the shrine after you kill him and Dagon will fix the Razor for you. After you take it the quest will end, but Dagon will still summon two Dremora to try to kill you as "one final test".

After completing this quest you can gain access to the inside of the shrine after taking a key from one of the Dremora that Mehrunes Dagon sends to attack you. Inside the shrine, the player will encounter two more Dremora but be rewarded with a room full of notable treasure.

Jason_Shugg wrote Full Detailed Walkthrough...

The Courier will approach you and give you a Dawnstar Museum pamphlet. (You must be at least level 20 for this to happen). Head to Dawnstar and go to Silus Vesuius' house. He will offer you a tour of the museum, and after the tour he will ask you to retrieve the three pieces of Mehrunes' Razor.

The hilt is in Morthal. When you meet Jorgen, the keeper of the hilt, he will deny knowledge. Convince him you know he has the hilt, and he will refuse to give it to you. Threaten, persuade, or pay him to gain access to the hilt. It is in a locked chest in his house to the west of the mill, so feel free to take it without even talking to him.

The shards of the blade of Mehrune's Razor is held in the vault of the basement of Cracked Tusk Keep. The key to the vault is on the bandit chief boss "Ghunzul". A hidden button on the wall opens the gate to the locked door opened by the key. Inside the vault, there are no enemies, but the way is trapped. A levers to the left and right of the pedestal open the 2. The "Become Ethereal" shout will let you run through the traps.

The pommel of Mehrune's Razor is at Dead Crone Rock. You will need to proceed through a series of tiers (in and out of the ruin) before reaching a hagraven at the very top who has the pommel. There is also a word wall nearby. You may find it necessary to walk all the way up to the word instead of standing slightly back as usual.

After retrieving the three pieces return to Silus and he will pay you a leveled amount of gold (more if brought all at once) and then ask you to meet him at the Shrine to Mehrunes Dagon. Upon arrival, he will be unable to get Dagon to repair the Dagger, so he will ask you to interact with the shrine. At this point, the daedric prince will demand that you kill Silus. Silus will ask you to spare him in return for 500 gold, saying that he will place the pieces of the Razor in a display case in his house. If you accept, he will give you the gold and run back to his house taking the broken dagger with him, while Dagon summons two Dremora to kill you.

If you choose to kill Silus, interact with the shrine after you kill him and Dagon will fix the Razor for you. After you take it the quest will end, but Dagon will still summon two Dremora to try to kill you as "one final test".

After completing this quest you can gain access to the inside of the shrine after taking a key from one of the Dremora that Mehrunes Dagon sends to attack you. Inside the shrine, the player will encounter two more Dremora but be rewarded with a room full of notable treasure.

I book marked this for when I'm lvl 20 (15 now)

happy i could help bro! have fun!!

dang i read first line and saw u must be lvl 20 and im 8 now. ah well ill read it once i use the exploits to get like 3 of my skills to lvl 100 lol. looks nice and detailed tho.

Jason_Shugg wrote happy i could help bro! have fun!!

I just got my full armor
Best place to mine is Gloombound Mine, and best place to get hearts is College of Winterhold buy em from the guy who sells them :p