About how much would it cost to build a computer, if I purchased everything, to build a tower with a reasonable amount of RAM and Hard Drive space, with all the capability a modern PC has (i.e., DVD/CD player, USB ports, Connection to a monitor, Bluetooth also, if possible)?
For a gaming pc the most expensive part is the video card. You can go from about 200€ to about 800€ IIRC.
For a modern everyday use pc it's the processor, around 100€. But you can find older models for less.
The least expensive... I guess the DVD drive, or the RAM sticks if you buy little of it. Should be around 20€.
Excluding peripherals, the least I think I could spend to assemble something that's not frustrating to use is 250€. 500€ for a good pc.
OS license excluded too.
About how much would it cost to build a computer with all the capability a modern PC has
I'd recommend going for 400-500€/$ if you can't spend too much. Also consider that monitor, keyboard, mouse and speakers are not calculated. Those would probably add 100+.
If you've got money to waste go for 1000.
Note that I'm in no way a professional in the hardware field, these are just my thoughts.
I spent $1,100 on my last build (~2 years ago). It's decked out with somewhere around 10 USB ports, 4 optional chassis fans, 3 external SATA ports, a SD card reader, a PCMCIA reader, 16 GB main memory, can't recall which processor though without looking in the case. It's either an i5 or i7 unlocked with an upgraded cooling system. At the time, SSD drives were still quite expensive as compared to what is available today, so I went with an 80gb SSD. All powered by the rock solid Asus Z77 sabretooth motherboard.
Quite sad that I hardly use it anymore thanks to my nexus.
I'd say 400-600 for a average rig and 600-800 for a decent gaming rig.
My current rig with 9550 phenom-i cost me 1100+ USD.
My built non-used rig with the i5-3570k + z77-g41 + hd7850 + 4GB gskill + 500 GB WD + 1080p cheap monitor + antec gx500 tower + mouse/keyboard + 530watt PSU + h_212_Plus + 4x 120mm antec tower fans cost me about 600 USD; felt I was ripped off on the 4GB of ram - in 2011 I purchased 32GB ram for 180 USD, if I was to purchase now it would cost me nearly double.
For 35 GBP, you can get a raspberry Pi. It's only of the cheaper computers our there.
It is a motherboard, ARM CPU, 512 MB RAM, 2x USB ports, 1x Ethernet, 1x HDMI, 1x Sound, 1x SD card (this is where the OS gets booted from).
There is no case, but you can make one from a margerine container. Use a USB hub to attach an external CD/DVD if you really need one. Use your current mouse/keyboard, and hook it up to your HDMI TV. That's the cheapest way have a new computer.
Website programming, Software Programming, Android Development (maybe iOS development), and eventually an OS (though I think by the time I have the experience to build an OS, I will have built another computer with newer technology).
The nessesary components are:
4. Video card
8. Peripherals (Wireless/bluetooth/ethernet/optical cards or drives)
This is also the order you want to choose things... Here are the details on what to get: CPU
It looks like you don't need anything overpowered. You could go with an i5 instead of an i7 to save on some cost here. Make this decision and the "socket" will determine which motherboards will be compatible.
This is the most important part. Find one with enough USB ports. Some have integrated graphics which is fine for you since you don't plan on doing anything graphics-heavy. If you want to save on the cost of a video card, look for these. Also ensure the one you select either has ethernet/bluetooth/wireless, or has enough PCI-express slots to add these in later. If you don't have integrated video, ensure you have at least one PCI-express x16 slot for a video card.
Don't need to spend much here, just ensure that the type (DDR2, DDR3, DDR4?) and rate match your processor/motherboard specs. Get a pair of chips of descent size. You can add more later if desired so you don't have to fill the motherboard right away.
Video card (GPU)
Only buy if you don't have an integrated chip or if you want good graphics. Spend as much as you want, but you don't need to go over $200. I like NVIDIA, but brand doesn't really matter unless you are in Linux and you might have problems with ATI drivers.
Get SATA III if you want speed. If you really need 1-2 TB, go for a conventional HDD. SDDs get really expensive at that size range. SDDs are MUCH faster, but more expensive. An option is to get a small SDD for your OS and a large HDD for your media.
Power supply (PSU)
The components you selected will have power ratings (at least CPU/Mobo and video card will). Get at least that size of power-supply. If your video card needs an extra power plug, make sure your PSU has that head available.
ATX is a full-sized case. If your MoBo is a micro-ATX, then you can get a smaller case but make sure your video card will still fit. Micro-ATX Mobo's also fit in ATX cases, so when in doubt, just go ATX.
Anything that isn't on your mobo already can be added as a PCI-express or USB extension. You can add extra USB ports, wireless card, bluetooth, etc. I use a USB DVD drive. You can also use a SATA DVD drive. For the DVD, don't spend extra money on SATA-III since the bottleneck is in the disk speed, not the bus-speed. SATA-I or SATA-II is fine. USB hubs are also good if you really need more.
Hope that helps. My first build took sooo much research, but after my 5th or 6th, it got easy. It's just about the realization that it's all about the Mobo and then it isn't complicated at all.
Note it'll probably be worse than what you're using right now, so keep that in mind. Your motherboard/components usually come with cables, so you don't need to worry about buying extra SATA cables or power cables. You WILL probably need a VGA/DVI cable though (but you probably already have one on your current monitor.