HEY COMPUTER GEEKS!!!

I have a problem with my laptop. One day my laptop suddenly goes banononononooz!! It takes about a minute and a half to finish the Windows progress bar and it takes about 3 minutes for the startup to finish, but it takes a jiffy to shut down my laptop. It takes Google Chrome and VLC Media Player about 3 minutes to open, but it only takes less than a minute to open other files and games. When I play games, it gets pretty lag. I already have avira! antivirus the oldest version and I scan weekly for viruses and stuff, defrag every 2 weeks, and error disk check every month. Can u please help me to completely repair my laptop by myself??

Additional info:
Version 5.1.2600 Service Pack 3 Build 2600
OS Manufacturer Microsoft Corporation
System Name COMPUTER_1
System Manufacturer Acer
System Model Aspire 3600
System Type X86-based PC
Processor x86 Family 6 Model 13 Stepping 8 GenuineIntel ~1496 Mhz
BIOS Version/Date Acer V1.10, 6/3/2005
SMBIOS Version 2.3
Windows Directory C:\WINDOWS
System Directory C:\WINDOWS\system32
Boot Device \Device\HarddiskVolume1
Locale United States
Hardware Abstraction Layer Version = "5.1.2600.5512 (xpsp.080413-2111)"
User Name COMPUTER_1\admin
Time Zone Taipei Standard Time
Total Physical Memory 768.00 MB
Available Physical Memory 110.71 MB
Total Virtual Memory 2.00 GB
Available Virtual Memory 1.96 GB
Page File Space 1.81 GB
Page File C:\pagefile.sys
Version 5.1.2600 Service Pack 3 Build 2600
OS Manufacturer Microsoft Corporation
System Name COMPUTER_1
System Manufacturer Acer
System Model Aspire 3600
System Type X86-based PC
Processor x86 Family 6 Model 13 Stepping 8 GenuineIntel ~1496 Mhz
BIOS Version/Date Acer V1.10, 6/3/2005
SMBIOS Version 2.3
Windows Directory C:\WINDOWS
System Directory C:\WINDOWS\system32
Boot Device \Device\HarddiskVolume1
Locale United States
Hardware Abstraction Layer Version = "5.1.2600.5512 (xpsp.080413-2111)"
User Name COMPUTER_1\admin
Time Zone Taipei Standard Time
Total Physical Memory 768.00 MB
Available Physical Memory 110.71 MB
Total Virtual Memory 2.00 GB
Available Virtual Memory 1.96 GB
Page File Space 1.81 GB
Page File C:\pagefile.sys


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