What computer should I get? - 1

I'm getting a new computer, I need it to be a decently powerful computer that can run applications like Photoshop and Sony Vegas and the occasional low demanding game like minecraft, I need it to be within £300 to £400 pounds ( $510 to $680 dollars)
How well would minecraft run?

What apps can you not get on a samsung phone?

So I have an iPhone 4s and I really don't like it and I'm considering changing to a Samsung Galaxy s4. Cuz I really only use my phone for my camera and pictures and the galaxy has a great camera. But I don't know anything about galaxy's and I wanna know can I still get all my favorite apps on a galaxy? Like Instagram, vine, Pinterest, Facebook, kik, snapchat, minecraft, survialcraft, high school story, flappybird?! Please help soon! Oh tell me should I switch to a samsung or stay apple?!

Can't break blocks in minecraft?

So every day I babysit this kid, and we usually play Minecraft together, but today when I got here he was fooling with the "Super Secret Settings". I got them back to normal, and now he can't break blocks. HE IS NOT IN ADVENTURE MODE <- I made sure to switch him to GAMEMODE 0, not 2. Just to make that clear since every answer has that there. He is in creative, and survival normally.

He is in a single player world, but even if I open LAN on my laptop he can't break blocks. Can anyone help?

Added (1). Also, all of the controls are correct as well. The option is on the left mouse button.

Is it a good idea to fight the Wither boss in the End in Minecraft?

My theory is that the Wither boss will attack the Enderdragon and the Endermen will attack the Wither, while I hide out in a little obsidian shack and wait for the carnage to ensue. Will they both attack me instead, and will the Enderdragon try to attack the Wither?

Could these computer specs handle minecraft/call of duty/bf4?

Western Digital WD 500GB 7200 RPM 16MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive
Team Elite 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10600) Desktop Memory
PowerColor AX7850 2GBD5-DHEV2 Radeon HD 7850 2GB 256-Bit GDDR5 PCI Express 2.1 CrossFireX Support Video Card
GIGABYTE GA-78LMT-USB3 AM3+ AMD 760G HDMI USB 3.0 Micro ATX AMD Motherboard
Operation System: Microsoft Windows 8 Pro - Pre-Installed Only
Corded Mouse & Keyboard Included
AMD FX-4130 Zambezi 3.8GHz Socket AM3+ Quad-Core Desktop Processor
ASUS DVD-Writer 24X DVD+R 8X DVD+RW 8X DVD+R DL 24X DVD-R 6X DVD-RW 16X DVD-ROM 48X CD-R 24X CD-RW 48X CD-ROM Black SATA Model DRW-24F1ST - OEM
LOGISYS CLK12RD2 12 inch Dual Red Cold Cathode Light
Cooler Master Elite 430 Red Edition - Mid Tower Computer Case with Windowed Side Panel and All-Black Interior
Thermaltake TR2 TR-500 500W ATX12V v2.3 SLI Ready CrossFire Ready Power Supply

Do i have a trojan horse?

So randomly 'My computer' opens about after 3-4 hours on my pc. It opens at least 10-11 times. Then just now the weirdest thing happened. I was playing minecraft. Then the my computer thing happened and when i right clicked on the group i pressed close group. The group finally closed and the close group option came up again. I pressed it and immediately it froze. Then after a while it closed all programs then my mouse turned into an hourglass and i couldn't click on anything. Then it came up with the windows shut down options (restart, shutdown etc) and i press cancel. This occurred after my pc prompted me to search for updates and it downloaded delta. Because i have Norton premier edition i pressed remove file because isn't the updates for xp stopped?

I have windows XP and i have FULL norton 360 premier edition.

Added (1). but i do have AV and also scanned it with NPE. Does this mean i have a rootkit virus or something serious

Can I replace my AMD Radeon HD 7310 graphics card with a 7770 without an issue?

I'm getting a bit into PC gaming and I have a pretty decent computer, but my graphics card is awful. I'm wondering if I can replace it without an issue? I'm not looking to play Skyrim or anything like that, just Minecraft, Goat Simulator, etc.

I have a
Gateway
Windows 7
64 Bit operating system
4GB of RAM
Processor: AMD E1-1200 APU with Radeon HD graphics 1.40 GHz

My lack of knowledge is unbearable, I know.