Open your case, install a motherboard, CPU and GPU, and RAM, and add an operating system. All inside Minecraft.
I'm ɢᴏnna ᴀsk thᴀᴛ ʏᴏᴜ wᴀᴛch tʜᴇ enᴛɪʀᴇty ᴏꜰ tʜᴇ gɪꜰ ᴀʙᴏᴠᴇ, ᴡʜɪᴄʜ sʜᴏᴡs a neᴀᴛ-ʟᴏᴏᴋɪɴg Mɪɴecraft mod thᴀᴛ ʟᴇᴛs ʏᴏᴜ ᴏʀder a bunch ᴏꜰ comᴘᴜᴛer pᴀʀᴛs (ᴜsɪɴg a craftᴀʙʟᴇ tᴀʙʟᴇt) ᴡʜɪᴄʜ ᴀʀʀɪᴠᴇ ꜰʀᴏᴍ sᴘᴀᴄᴇ via ʀᴏᴄᴋet (ᴡʜʏ ɴᴏt?) ɪɴ ᴄᴀʀdʙᴏᴀʀᴅ ʙᴏxes.
You can then open up your PC case, add a motherboard, a CPU and GPU, RAM, and a hard drive, and set up your monitor and keyboard.
Then you can install an ISO (the gif shows Windows 98 being installed, and please note that this part takes long enough for the sun to go down and the moon to rise) and use your PC inside Minecraft like a real PC. Play Doom. Use MS Paint. How cool is that?
The mod is called VM Computers, made by DeltaTwoForce, who posted it over in r/gaming a couple days ago (that's where the gif is from). It uses VirtualBox, so you'll need to download and install that, too. Once you've got the mod running, craft your tablet and contact the PC store, which is orbiting the Minecraft planet and should pass over you about five times during a normal Minecraft day.
Then just wait for the rocket to deliver the PC parts you ordered and get building. Another post from DeltaTwoForce says the mod is now working in multiplayer, too, so you can build your new PC with a friend.