Just got a desktop from Ebay for my kids. AMD Bulldozer, 12GB ram, 500GB 7200rpm HD with a decent case, gigabyte mb and nice graphics card with windows 7 os. Less than £400 which compared to the costs for the bits individually was a nice deal.
I swapped out the PSU with a better one reducing the cabling and swapped the cpu fan also replacing the cheap compound with a higher spec to prolong the life of the machine.
I use windows 7 laptop for a number of work reasons non programming related its similiar to this one here http://www.notebookguru.de/en/Notebooks/Guru-STORM-IV.html with 2 x 360 SSD drives one for the os and one for programs.
You get what you pay for. Its best to look at benchmarks for your needs some i5 cpu's out perform i7 cpu's for example. Do your research and know what your looking for.