laptop stays at welcome screen. only the cursor visible and it is enla

Run a full scan, then continue with steps in order from the top.

ok so finally downloaded the windows defender offline to usb. chose usb in the bios for booting then started laptop. it is now on the windows defender offline with a load bar underneath it screen. has been on this screen for a while. how long should i wait for it to start?

actually it has just stopped and given an error. it says windows defender cannot be started please contact support. error code 0x8007045d

Try Malwarebytes in Safe Mode, or one of the other Bootable AV's given. Some of these can also rescue your files, or there is a step for that if necessary.

okay so i downloaded the malware bytes and remotely scanned the harddrive using my other computer. these are the results

Malwarebytes Anti-Malware (Trial) 1.70.0.1100
Malwarebytes : Free anti-malware download

Database version: v2013.03.07.14

Windows 8 x64 NTFS
Internet Explorer 10.0.9200.16484
Colin :: COLIN [administrator]

Protection: Enabled

07/03/2013 21:09:37
mbam-log-2013-03-07 (21-09-37).txt

Scan type: Full scan (F:\|)
Scan options enabled: Memory | Startup | Registry | File System | Heuristics/Extra | Heuristics/Shuriken | PUP | PUM
Scan options disabled: P2P
Objects scanned: 202142
Time elapsed: 20 second(s)

Memory Processes Detected: 0
(No malicious items detected)

Memory Modules Detected: 0
(No malicious items detected)

Registry Keys Detected: 0
(No malicious items detected)

Registry Values Detected: 0
(No malicious items detected)

Registry Data Items Detected: 0
(No malicious items detected)

Folders Detected: 0
(No malicious items detected)

Files Detected: 0
(No malicious items detected)

(end)

I would verify this with one bootable AV scan. If clean or you wish to skip this you can move on to the next steps in order. Keep us posted on results.

ok so nothing works. think im just gonna reinstall windows.

ok so I reinstalled windows 7 but have encountered problems. I have started a new thread here:
new installation not connecting to internet