I was using Win 98SE which was performing well - but since after I installed XP on my PC, it is slow in all the operations. It takes much time to start, work, and at shut down. Some of the programs also freeze without responding. What can I do to regain it's speed?
this is most likely to be your pc specifications are very low on your pc and since xp is a lot more demanding to windows 98 you computer is struggling.
what is the spec of your computer?
Yep, and if it's because of your low specs you need to upgrade your PC.
You might just have to upgrade your RAM. If you can no longer upgrade your PC you'll have to either go back to Win98 SE or try Windows 2000. You might also want to consider getting a new PC, that is if you can afford it. However, a decent PC costs ~$300 USD (if you see one on sale) nowadays so it's not too expensive.