Well P4 do run very hot. And if your system still boots up and runs fine, it probably isn't fried. I would do a few things first, which mainly involve your HDD. Clean the HDD of whatever you don't need and free up some space. Defragment for HDD (can be found under Accessories --> Systems tools --> Defrag. (note: if you have a SSD, don't defrag it, only HDD).
Other problems could be needing more memory, or other parts aging. Another thing is that P4 is pretty outdated technology, and if you can, look into upgrading/building a new PC. My current computer at my work is a P4 running at 2.8GHz, and i can barely have 3 windows open and type in word at the same time, or it will freeze for 10 seconds.