I removed my HDD from my PC and put it into another old pc. Then I replaced it again in the original. Now the mouse won't work

did you ghost copy the windows 7 to the new drive or reinstall with cds

Unable to FORMAT the HDD in the device? Perhaps remove the drive - hook it up to a working PC temporarily, and using a partition software program or you could burn a CD (I use PartitionWizard), delete any or all partitions on the new 160GB WD and make that drive UNALLOCATED and UNFORMATTED. Apply the actions as needed - only to that drive (this will at least allow your unit to recognize it properly). Once done, remove the drive from the PC, and put it back into your recorder - see if it recognizes it this time, then try and format it (in accordance with the type of file system the unit uses - which may differ from that of a PC). Replacement drives should be formatted to suit the unit they are intended for AFTER they are fitted, not before. Otherwise you run into compatibility problems (e.g. the drive won't allow recording/doesn't read etc., but might work in a PC). If this is the case, it may explain greyed out options and not being able to record to it. If you still have the original drive, check the jumper setting to be sure. If both old and new are set to CS - leave them as is - don't change that.

1.driver is not compatible
2.mouse cable check and next ,all mouse doesn't work because hd failure.

Press and hold your power button till it shuts down.
this is a common crash, youll get one every now and again, not to worry unless it happens daily.

try to remove the mouse from the port and put it again. Then restart the pc so that the USB port for mouse will be updated. Try other ports if it is not working, otherwise replace your mouse if it still did not work..

Remove the battery off and keep aside from within the mouse. Now disconnect the USB - optical detector to the PC. Shut down the PC . Replace battery once again and power the PC, then connect the USB to see if the mouse is detected.
If not remove off installed software of the optical device and reinsert once again so that it gets detected.

some viruses affect mouse driver or the interrupt signal for the mouse.
i suggest checking your pc from virus ,

Here are the rates of what they are selling average used
INTEL CORE 2DUO
$100
2gb ram
depends on type- ddr2 would day around $30
320 gb hdd again depends on type- SATA around $40
dvd burner $20
keyboard mouse combo $20
20" monitor 75

INCREASE THE BRIGHTNESS OF YOUR SCREEN THROUGH PROPERTIES OF SCREEN AND CHANGE OLD KEYPADS AND MOREOVER REMOVE DUST STICKED BELOW YOUR MOUSE.

check to see if your ram has not losse, had the same problem with a mates computer.