Hi , i've got a dual boot computer with win7 and home XP ( win7 the one i'm using now... ) . The problem is that the mouse and keyboard stopped working at login screen at bootup in XP, it's usb keyboard and mouse. This happened after i've got a virus warning the before shutdown and boot up. The computer worked after the warning. But the day after at bootup checkdisk started to repair files, but at the day before when i got the virus warning iv'e also got a powercut and bootup so that could be one reason it repaired files. Any help thanks.
To solve your problem put win xp cd and boot from cd . then select repair windows in this process it replace curated windows file. then your mouse and keyboard works.
Might be simple, try putting them in different ports, often the drivers are installed again. Also defo get rid of your virus and run some online scans to be sure. There are a number of antimalware programs you should probably scan with as well just in case there is some leftover crap.