I have Installed BuildCraft with no other mods but when i start Minecraft, i get an error message named "IDConflicts" in my .minecraft folder with the following text inside:

Blocks

150: comparator from Unknown - miningWellBlock from BuildCraft|Factory
151: daylightDetector from Unknown - plainPipeBlock from BuildCraft|Factory
152: blockRedstone from Unknown - autoWorkbenchBlock from BuildCraft|Factory
153: netherquartz from Unknown - machineBlock from BuildCraft|Factory
154: hopper from Unknown - markerBlock from BuildCraft|Builders
155: quartzBlock from Unknown - fillerBlock from BuildCraft|Builders
157: activatorRail from Unknown - builderBlock from BuildCraft|Builders
158: dropper from Unknown - architectBlock from BuildCraft|Builders
170: hayBlock from Unknown - null from BuildCraft|Silicon
171: woolCarpet from Unknown - pathMarkerBlock from BuildCraft|Builders
172: clayHardened from Unknown - blockHopper from BuildCraft|Factory
Suggested Ranges: 2268-4094 (1827 IDs), 1532-2255 (724 IDs), 422-1022 (601 IDs)

Please help!!!

One of the following options probably applies:

A. your playing single player and you need to check the config file and update it manually to whatever ids you want to make it work.

or

B. your going to play multiplayer and need to get a copy of the config file from someone on that particular server.

Assuming you have the right minecraft version coupled with the right buildcraft version, I would "hope" this problem wouldn't occur. But I just gave you the workaround so hope that helps.

As AlexCory said, make sure that you have the right buildcraft version for the minecraft version you are using. From the looks of it you're using a really old config file

Your BC config overlaps with newer vanilla blocks added in recent versions. You need to adjust your configs (or delete them and start over as current defaults don't overlap with vanilla).

I use BuildCraft 4.1.0 with Minecraft 1.6.2 and the newest Forge version!
I want to use it only in single player.

Ok, thanks!