Ok here we go. so i have done this before so i know it works.
first take all leads out of the back of your p.c. lay on it's side and take of the side panel. do this with both your new and old p.c.
inside you new p.c you are looking for this. the lead that go's to the Harddrive. it should have a second bit coming of it. it should be marked on the connector P4 if you have this then you can do what i'm about to show you.
once you have found the right connector. do the following. take out the Harddrive from your old pc with this lead still on it.
looking inside your new pc for a spare slot to place and fix with the screws that you took out from the old one. you then should have something like this.
connect the spare P4 connector to the Harddrive from your old pc and the lead that was on it connects to this slot on the motherboard.
once all connectors are in place they should look like this.
Before you do anything look for all the connectors and make sure you know where they are all going. and make sure you don't rock any of the connectors side to side. they should just push in easy.
once this is all done. you can then place the side panel back on and wire up your pc to the power ready for the next part.
Once your p.c is turned on. it mite say downloading drivers or something like it would with a new USB stick.
ok so this is the easy and fun bit. it were you get all your files back.
Click on the start menu at the bottom left of your screen. the click on Computer/ then you should see this.
this is your old Harddrive you just put in. double left click on it. you should then see this.
click on users. you should then see this.
it should say what the name of your old pc was called. click on it and then you should see all you folders ect
once you have found everything you need. copy and paste to a USB Stick or something like that.
once you have got everything you need. you can either take the Harddrive you put in from your old pc. or you can leave it in for extra storage space. but you will have to Format it. you do this by just going back to Start Menu/Computer/Right Click on the Harddrive and then Format. this will delete everything ready to use as storage space.
Hope this works for you. as long as you have all the leads and connector you should be ok to get all you stuff from your old pc. :) XX