CPU fell on floor now windows won't load. How can I tell if he'd is hosed or can be fixed?

Try to boot it from safety mode.
and try to restore your system first.
If the restoring is failed, boot safety mode again and back up your files.
If you can't boot your laptop from safety mode, use anti virus program CD like norton.
Mostly, your system is messed up by adwares, spywares, and virus.
If all things fail, you should check your HD.

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Try changing the boot order to HDD.

Somehow your MBR (Master Boot Record) likely got corrupted or possibly your hard drive went bad coincidentally.

Simply, you will start your computer from your Windows CD/DVD install disk, then when at a DOS prompt ( D:\ ) you will then type: FDISK /MBR (press enter).

Find your Operating System install DVD and start your computer with it, then follow instructions within this discussion:
Restore Windows XP MBR without Windows XP disc

Alternatively, review my search results for other instructions:
fdisk mbr windows xp Google Search

Most of the boot up of problem because of hardware problem, registry missing or crashed, file deleted or changed.
You can boot up your Windows with Tenorshare Data Recovery WinPE.It allows users to burn ISO file to CD/DVD/USB flash drive directly.
Step 1: Download Tenorshare Data Recovery WinPE in any available computer (not from PC that can't boot up). Then launch it.
Step 2: Insert CD/DVD/USB flash drive to the computer, choose ISO image file. Here we take USB flash drive for example. Then burn ISO file into flash drive.
Step 3: Insert the burned flash drive to the unbootable PC. Run computer and press "F2", "F10" or "Delete" to enter BIOS setup.
Step 4: Use the arrow keys to select Boot tab, select Boot Device Priority and press Enter. Please choose 1st Boot Device to USB, and then press F10 to save setting. Now,you can boot up your PC.
If you have a backup for your Windows then perform a system restore to fix it.If not,reinstall it.If you have no backups for all your data,you can use Tenorshare to retrieve data under any boot up problem.You can get it from http://www.any-data-recovery.com/product/datarecoverywinpe.htm
Here is tutorial to guide you how to do --How to Recover Data from Computer Won't Boot Up?-Windows Data Recovery.

its simple just farmat and restor your pc

try to boot into safe mode with a lower resolution screen

the hardrive has failed take it out and have it checked or replace

If you bought a new hard drive (meaning the internal hard disk), it won't have anything on it. If you just install it and try booting your computer, there won't be an operating system to load. The BIOS (the operating system built into the motherboard) is set up to try loading the operating from connected devices in a certain order. Usually it tries the optical drive first, then the hard drive, and finally it tries to boot over a network connection. The media test failure message means it tried that last resort and still didn't find an operating system, and it's telling you that maybe you have a bad network cable.

You'll need to reinstall your operating system and applications so that the computer will start normally. If your computer came with a restore disc set, or you made a set yourself, you'd use those. If you don't have restore discs, you can do a fresh installation of Windows from CD. You need to find the disc for the version that came installed on your computer, since you'll need to use the product key from the sticker on the bottom. Drivers and utility programs you can download from Compaq's (HP, actually) support and drivers website.

Once you've got a bootable Windows system on the new drive, you won't get that strange message any more.

RY THIS FIRST Hold down FN KEY and POWER Button for 3 Secs to go in Diagnostics Mode (works on almost all Dell Laptops) and run the full test you'll find something wrong if its a internal issue (even if its a hard drive issues), see if that fixes it, but I'd check the CPU HS Fan (the slots where air comes out)just blow in there and you'll see dust come out, clean it out with Air Can or Air Hose at 60PSI to prevent it blowing your blades up on the fan. If its not a hard drive or cooling issue, might want to try the Memory check (Dell has laptops have memory issues from time to time) Hope this helps!

put in a windows disk,,cd,,,,,restrt cpu,,,push esc button boot options,,,also check sony website may need a bis update ,,