SL clean install freezes adding personal date

Here is the machine details. http://www.macupgrades.co.uk/store/serial.php?mod_num=MB402LL-A

Purchased as refurbished when trying to start it was so painfully slow, could only type one or two digits before it froze., as we got this for my daughter she was trying to use it, she did a factory reset. then the problems start.

The company where we purchased it do not want to know now. On talking with Apple support we purchased a dvd of SLeopard . the install went seeemingly OK, but still painfully slow

I have only ever worked on windoze so a little lost, I upgraded the ram from 2 to 4gig of the exact type, Made no difference, next I replaced the hard drive, and tried a clean install. I followed instructions I found on here and still the same problem. I formated again zerod out data, set Guid correctly, checked drive permissions etc And tried again, I got the furthest into adding personal info (forgot the exact section) know I got to language, keyboard, network, Apple ID, and a couple more and it just sits there and sits there.

Not being an expert but by process of elimination, I ask the question . Is it the DVD ? or some other issue with hard ward ? My next idea would be to check the paste with cpu and heatsink. and go through all leads to make sure of good connection.

If anyone is kind enough to help bail me out, please do not get me lost on jargon I have limited OS knowledge

Thinking of jumping on a Bus and taking to Apple store 25 miles away seeing if they could advise, but it is already standing at over £300 spent and still not usable, a little reluctant to keep throwing money at it