1] Your Pc Must have 256MB RAM , 512 MB Cache , Intel Pentium 4 Processor, 40 GB HDD. These are the minimum requirements.

2] If you see a 'virtual memory low' message then increase its virtual memory. To increase virtual memory,
Go to My Computer->Properties->Advanced->Performance Settings->Advanced->Virtual Memory->Change->Select the appropriate drive->Custom size->set appropriate level(our it is 600(min.) & 700(max.)->Ok.
3] Increase 'Visual Performance'. Go to My Computer->Properties->Advanced->Performance Settings->Visual Settings->Custom->Select only the following options.
a)Slide taskbar buttons.
b)Smooth edges of screen fonts.
c)Smooth-scroll list boxes.
d)Use a background image for each folder type.
e)Use visual style on windows and buttons.
4] Don't keep unwanted/extra fonts. To remove extra fonts, Go to Start->Settings->Control Panel->Fonts.
5] Your Desktop Wallpaper & Screensaver consume a large amount of disk space. Select the 'None' option for both wallpapers & Screensavers.
6] Avoid keeping DEMO Games.
7] Uninstall the unwanted Softwares.
8] Use Registry Cleaner to keep your registry clean(without errors).
9] Try to keep Music and pictures files in the folder specified by windows itself. 10]Use Hybernating Option for Quick windows start. To active Hybernating follow the following steps.
Desktop->Properties->Screensaver->Power->Hybernating->Enable Hybernating->Ok.
11] Keep your Dektop clean with unwanted icons.
12] Use Intel Application Accelerator to speed up your disk access,
13] Memory management (at least 512MB RAM Required). This allow XP to keep data in Memory instead of paging section of RAM.
Go to->Start->Run->regedit->HKEY_LOCAL_MACHINE->SYSTEM->CurrentControlSet->Control->Session Manager->Memory Management->Double click it->DisablePageingExecutive->Double Clik it->Set value to 1.
14] Disable Yahoo Messenger, Google Talk, and other unwanted programs from startup. (You can use registry editior to do this.). Because they do not appear in normal Startup Option.
15] Disable indexing files service (only if you do not use search option regularly). To do this follow the following steps.
Go to My Computer->Select the drive for which you want to disable the indexing service->Properties->Unselect 'Allow Indexing Service'->Ok.
16] For Windows XP, You must use NTFS partition. FAT partition is less supportive for Windows XP.
17] In BIOS, Select first booting device as your HDD. 18] Setting Priority High for a particular program.
Open Task Manager->Processes->Select the desired Program->Right Click->Set Priority->High->Ok.
This Priority set if for current session. Once you restart your system then its priority will again be Normal.
19] Keep deleting your Temporary Internet Files in regular intervals.
Go to Windows Drive (c: or d:)->Select the User->Local Settings->Temporary Internet Files
20] Empty your browser's cache in regular intervals.
21] Avoid keeping Movies in your PC.