I reformatted a used laptop(dell latitude c840). the mouse touchpad responds sluggish and then stops responding altogether. same thing when I connect a usb mouse. Could the wrong ac adapter be responsible for this? using a 70watt, but boot screen warns that 90watts are required for optimum performance. Everything else works on the laptop, and I don't want to spend more money if I don't have to. Thanks everybody

If the laptop has no main battery and the laptop will run on just the AC adapter, or if it does have a main battery but can no longer run the laptop on it's own for more than a very short time, yes, you probably need an AC adapter that provides more power. If the touchpad (uses very little power) and USB mouse (the USB port can provide up to 500ma but most mice use under 25ma) are not working properly due to lack of power, it is very likely your cpu is not performing to it's full potential either. Look up the part number for the AC adapter for your model on the Dell site, or search on the web for one for your model - if it is a common one, you can probably get a used one or even a new clone or universal one cheap. On the other hand, old touchpads often do not work properly. (If you clean it using isopropyl (rubbing) alcohol, it may as take as long as a full day before it works normally again). Whenever you load Windows from a regular Windows CD (or DVD) from scratch, after Setup is finished you must load the drivers for the mboard, particularly the main chipset drivers, in order for Windows to have the proper drivers for and information about your mboard hardware, including it's AGP or PCI-E, ACPI, and hard drive controller support. If you have a generic system and have the CD that came with the mboard, all the necessary drivers are on it. If you load drivers from the web, brand name system builders and mboard makers often DO NOT have the main chipset drivers listed in the downloads for your model - in that case you must go to the maker of the main chipset's web site, get the drivers, and load them. In your case, you also need to load the proper drivers for any other devices the laptop has that Windows doesn't have built in drivers for. If that's your case, you probably have unknown devices or entries for devices that are not working properly in Device Manager. Your touchpad may or may not work properly with regular PS/2 mouse drivers. Dell should have those drivers available on their website in the downloads for your model.