Maybe because of low Memory some of your Applications are not running properly.
Try the following and you'll surely speed up your computer -->
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Step 1 -->
Increasing your Virtual Memory. For that follow these steps -->
1.Right Click My Computer > Properties
2.Go to Advanced
3.In the Performance box click on Settings
4.Go to Advanced
5.In the Virtual Memory Box click on Change
6.Click on Custom Size
7.Set Initial Size to twice of your RAM i.e 1024
8.Set the Maximum Size to twice of your RAM i.e. 1024
9.After that Click on Set
10.Click OK /Apply , then Restart
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Step 2 -->
Turn off Services that you don't use.
To turn off services do the following -:
Go to start--->run--->msconfig
Go to the startup tab and uncheck all unnecessary items that start during
the startup .
You can incheck the following services -->
Alerter
Background Intelligent transfer service
Clipbook
Computer Browser
Error Reporting service
Help and support
Indexing service
IPSEC services
Messenger
Netmeeting Remote desktop sharing
Network DDE
Network DDE DSDM
Performance Logs and Alerts
Portable Media Serial No.
QoS RSVP
REmote Desktop Help Session Manager
Secondary logon
Server
SmartCard
Smart Card Helper
SSDP Discovery service
system restore service
TCP/IP NetBIOS Helper
Uninterruptile Power Supply
Universal Plug and Play Device Host
WebClient
Windows TIme
WIreless Zero COnfiguration
WMI Performance Adapter
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Step 3 -->
Speed up your Menus
Go to start-->run--->regedit
navigate to HKEY_USERS.DEFAULTControl PanelDesktop
From the right double click the DWORD named MenuShowDelay. Change its value from 400 to a very low value like 25 or something.
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Step 5 -->
Also turn off all the eye candy that XP offers.To do that follow these
steps-->
1.Right Click My Computer > Properties
2.Go to Advanced
3.In the Performance box click on Settings
4.In the Visual Effects Tab click on Adjust For Best Performance
5.Click Ok Apply.
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Step 6 -->
Run a Full System Anti-Virus Scan using Norton,Mcafee,etc and Spyware scan using SpyBot Search & Destroy.
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Step 7 -->
Do not forget to Defragment your Drive to boost performance.For faster defrag use third party applications like O & O Defrag Pro, Diskkeeper, etc.
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Also as someone suggested above check whether all System Files are intact.
To check do the following with the XP CD in the Drive :
1.Click Start > Run
2.Type : sfc /scannow
Hope it helps...
Regards,
Tanmay